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Title: The anatomy of the domestic fowl

Author: B. F. Kaupp

Release date: August 8, 2023 [eBook #71368]

Language: English

Original publication: Philadelphia: W. B. Saunders Company, 1918

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*** START OF THE PROJECT GUTENBERG EBOOK THE ANATOMY
OF THE DOMESTIC FOWL ***

Transcriber’s Note:

New original cover art included with this eBook is
granted to the public domain.

The Anatomy
of the
Domestic Fowl

By
B. F. Kaupp, M. S., D. V. M.
Poultry Investigator and Pathologist in the North Carolina Experiment Station, State
Department of Agriculture, and the State College of Agriculture; Formerly Director of
Anatomy Laboratory, Kansas City Veterinary College

Illustrated

Philadelphia and London

W. B. Saunders Company
1918

Copyright, 1918, by W. B. Saunders Company

PRINTED IN AMERICA

To
DAN T. GRAY, B. S., A. B., M. S.
Chief, Animal Industry Division, North Carolina
Experiment Station
As a Token of Respect and Gratitude This
Volume is Dedicated
By
THE AUTHOR

FOREWORD

Advanced work in the study of poultry husbandry is now being done in
this country, to a greater or less extent, at all the two score and more
Agricultural and other Colleges and Experiment Stations. From these
institutions comes the demand for a text-book on the Anatomy of the
Domestic Fowl. No complete text-book on the subject, up to the present,
has existed. It is with the hope of meeting the demand that this book is
published.
In supplementing the information gathered from the books and articles
listed in the bibliography, the author has spent much time and effort in
obtaining the matter here presented. As this, however, is the initial complete
text on the subject necessarily much remains to be added and corrected. The
author would welcome suggestions and corrections from any one into
whose hands the book may come.
B. F. Kaupp.

The North Carolina State College of Agriculture,
West Raleigh, North Carolina,
September, 1918.

CONTENTS

OSTEOLOGY

Page
Osseous Structure 17
Classification of Bones 20
Composition of Bone 21
Skeleton of the Fowl 21
Axial Skeleton 23
Cranium and Face 23
Occipital 25
Ethmoid 27
Sphenoid 28
Frontal 29
Parietal 29
Temporal 29
Premaxilla 31
Maxilla 32
Nasal 32
Lacrimal 32
Palatine 33
Pterygoid 33
Zygomatic 33
Vomer 33
Jugal and Quadrato-jugal 33
Quadrate 34
Inferior Maxilla 34
Turbinate Bones 34
Hyoid 35
Vertebral Column 35
Cervical Vertebræ 35
Atlas 37
Axis 37
Dorsal Vertebræ 39
Lumbo-sacral Vertebræ 39
Coccygeal Vertebræ 41
Ribs 41
Sternum 42
Appendicular Skeleton 43
Shoulder Girdle 43
Fore Limb 44

Pelvic Girdle 48
Hind Limb 50

ARTHROLOGY
Kinds of Joints 56
Movements of Joints 56
Ligamentous Structure 57
Ligaments of:
Ear 58
Jaw 58
Vertebræ 58
Ribs 59
Sternum 59
Shoulder-joint 61
Elbow-joint 61
Carpal Joint 62
Finger 64
Pelvis 65
Hip-joint 65
Knee-joint 65
Tibio-metatarsal Joint 69
Toes 69

MYOLOGY
Kinds and Structure of Muscles 70
Fascia 71
Muscular Nomenclature 71
True Dermal Muscles 71
Dermo-osseous Muscles 73
Muscles of the Head 76
Muscles of the Tongue 79
Cervical Muscles 81
Muscles of the Air Passages 86
Superior Larynx 86
Inferior Larynx 86
Sternal Muscles 90
Abdominal Muscles 90
Dorsolumbar Muscles 92
Coccygeal Muscles 93
Costal Muscles 96
Anterior Pectoral Muscles 99

Pectoral Muscles 100
Muscles of the Scapular Region 101
Muscles of the Brachial Region 104
Muscles of the Forearm and Hand 105
Digital Muscles 109
Muscles of the Posterior Limb 111
Tibial Group of Muscles 117
Muscles of the Eye 124
Muscles of the Ear 128
Functions of Muscles 128

SPLANCHNOLOGY
Digestive Apparatus 135
Mouth 135
Tongue 139
Pharynx 141
Glands Adjacent to Mouth and Pharynx 141
Esophagus 142
Crop 142
Stomach 143
Proventriculus 143
Gizzard 145
Small Intestine 147
Large Intestine 150
Cæca 151
Cloaca 151
Course of the Food 152
Accessory Organs of Digestion 152
Liver 153
Pancreas 155
Spleen 155
Abdominal and Pelvic Cavities 156
Peritoneum and Mesentery 156
Relations of the Visceral Organs of the Domestic Fowl 158
Relations of the Visceral Organs of the Baby Chick 165
Uro-genital System 169
Urinary Apparatus 169
Kidneys 169
Ureter 174
Male Generative Organs 175
Testicles 175

Vas Deferens 178
Female Generative Organs 178
Egg 180
Oviduct 182
Parts of the Oviduct 183
Ligaments of the Oviduct 188
Ductless Glands 190
Thyroid Gland 190
Thymus Gland 190
Adrenal Gland 191
Respiratory Apparatus 193
Nostrils and Nasal Chambers 193
Pharynx and Superior Larynx 193
Trachea 194
Inferior Larynx 194
Bronchi and the Lungs 195
Air-sacs 199

ANGIOLOGY
Circulatory Apparatus 206
Heart 206
Structure of the Heart 207
Blood-vessels 209
Structure of the Capillaries and Arteries 209
Structure of the Veins 211
Arterial Trunks 211
Branches of:
Arteria Brachiocephalica 213
Arteria Carotis Cerebralis Interna 214
Arteria Carotis Externa 214
Arteria Carotis Facialis 214
Aorta Posterior 224
Venous Trunks 233
Branches of:
Venæ Cavæ Anteriores 234
Vena Jugularis 237
Vena Occipitalis Externa 239
Venous Sinuses of the Head 239
Veins of the Brain Cavity 241
Veins of the Neck 242
Branches of the Vena Subclavia 243

Veins of the Dorsal Region 243
Veins of the Thorax 244
Veins of the Fore Limb 245
Branches of the Iliaca 246
Branches of the Vena Iliaca Interna 247
Posterior Vena Cava 247
Veins of the Posterior Extremity 248
Branches of the Vena Cava Posterior 248
Veins of the Caudal Region and Pelvic Cavity 250
Veins of the Truncus Vena Iliaca Communis 252
Visceral Veins of the Posterior Vena Cava 252
Lymphatic System 254
Blood and its Functions 257
Fate of the Erythrocyte 261

NEUROLOGY
Nervous System 264
Cranial Nerves 265
Olfactorius 265
Opticus 267
Motoris Oculi 267
Patheticus 268
Trifacialis 268
Abducentes 270
Facialis and Acousticus 271
Vagus Group 272
Glosso-pharyngeus 272
Vagus or Pneumogastricus 273
Accessorius Spinalis 274
Hypoglossus 274
Spinal Cord 275
Structure of the Cord 275
Structure of the Nerve Trunks and Ganglia 277
Spinal Nerves 281
Brachial Plexus 282
Lumbo-sacral or Crural Plexus 285
Brain 288
Coverings of the Brain 288
Structure of the Brain 289
Divisions of the Brain 290
Sympathetic Nervous System 297

Functions of the Nervous System 300

ESTHESIOLOGY
Sense Organs 303
Sight 303
Hearing 305
Smell 307
Taste 307
Touch 307
Structure of Appendages 309

EMBRYOLOGY
Spermatogenesis 318
Oögenesis 319
Fertilization 319
Outline for Laboratory Study of the Chick 330
Living Embryo 330
Preparation for Study of Entire Embryos and Sections 330
Points to be Observed in the Study 332
Derivatives of the Germ-layers 342
Preparation of Structures for Study 343
Directions for Dissecting Muscles 343
Directions for Study of the Viscera 344
Directions for Study of the Arteries 345
Study of the Structure of Bones 346
Special Technic for Dissection of Cranial and Spinal Nerves 347
Directions for Study of Soft Structures 347
To Stain Sections of Liver for Study of Kupffer Cells 349
To Prepare Anatomical Specimens for Museum 349
To Make Specimens Transparent 350
Equipment for the Dissection Laboratory 351

Bibliography 353
Index 355

ANATOMY
OF THE
DOMESTIC FOWL

OSTEOLOGY

Osseous Structure.—Bone is structurally modified connective tissue which has
become hard by being impregnated with calcium salts.
Kinds of Bone Tissue.—There are two kinds of bone tissue: substantia compacta, or
compact bone tissue; and substantia spongiosa, or spongy, cancellous bone tissue.
Compact Bone Tissue.—The compact bone tissue forms the hard outer layer of all
bones. It is thickest in the shaft and becomes thin toward the extremities. Through the
compact bone tissue approximately parallel with the longitudinal axis of the bone, run
canals called Haversian canals, through which pass blood and lymph vessels for the
nourishment of the bone and nerves. The Haversian canals are surrounded by concentric
lamellæ. The spaces between the cylinders thus formed are filled with interstitial lamellæ;
and both the exterior surface of the bone and the interior surface surrounding the
medullary canal, are built up of peripheral, or circumferential lamellæ. Between the
lamellæ, somewhat irregularly placed, are minute reservoirs, called lacunæ, which contain
bone corpuscles. From the lacunæ radiate minute canals, or canaliculi, which maintain
circulation through the bone substance, and which communicate with the Haversian
canals. Complex anastomoses exist among the canaliculi. Still other channels for the
passage of blood-vessels are Volkmann’s canals which pierce the peripheral lamellæ, thus
allowing vessels to pass from the periosteum to the Haversian canals. Similar channels
afford communication between the inner Haversian canals and the medullary cavity.
The entire structure composed of an Haversian canal, its surrounding lamellæ, lacunæ,
and canaliculi, with their contained vessels, is called an Haversian system.
Cancellous Bone Tissue.—The cancellous bone tissue forms the bulk of the short, flat,
and irregular bones and of the extremities of the long bones. It consists of delicate bony
plates and spicules, which intercross in various directions. The spaces between these
plates and spicules, called cancelli, are occupied by marrow except in the bones that are
pneumatic. The blood-vessels, lymphatics, and nerves course through this marrow but are
not arranged in an Haversian system.

Fig. 1.—Longitudinal section of compact bone
of the femur of the hen. 1, Haversian canals. 2,
Lacunæ with their canaliculi.

The Periosteum.—Covering the surface of bone, except at the articular surface where it
is covered with cartilage, is a membrane, the periosteum, which consists of two layers: an
outer, fibrous, protective layer, and an inner, cellular, osteogenic layer. The outer layer
consists principally of white fibrous tissue. The inner layer contains many more
connective-tissue cells, which gradually become more closely aggregated as we proceed
toward the osseous surface; but there is no sharply defined line of demarcation between
the two periosteal layers.

Fig. 2.—Transverse section of compact bone of
the femur of the hen. 1, The lacunæ and
canaliculi. 2, The periosteum.

Fig. 3.—Transverse section of compact bone of
the femur of the hen showing the lacunæ and
canaliculi under high magnification.

The periosteum is firmly attached to the bone by trabeculæ of fibrous tissue, called the
fibers of Sharpey. These fibers of Sharpey penetrate the bone at right angles to its surface
and carry blood-vessels.
Marrow.—There are two kinds of marrow: yellow, or medulla ossium flava, and red, or
medulla ossium rubra.
The yellow marrow occurs in all bones except the femur and proximal portion of the
tibia of adult fowls. It is composed of a network of fibrous tissue carrying blood-vessels,
fat cells, and myelocytes, or marrow cells.
The red marrow is found throughout the femur and the proximal portion of the tibia,
and in a few of the pelvic bones and vertebræ in the adult fowl, and in certain other bones
of the baby chick. Red marrow consists of a delicate network of connective tissue
supporting a dense capillary plexus, a small amount of fat, and numerous cells. The
cellular elements of red marrow consist of marrow cells which contain large nuclei and
possess ameboid movement, red blood cells, giant cells containing one or more nuclei, and
various kinds of leucocytes, including eosinophiles, mast cells, and also osteoclasts.
Growth of Bone.—In the baby chick, only the shaft and a portion of the extremities of
the long bones are thoroughly ossified, the extreme ends, and of the femur most of the
articular head, being cartilaginous. The bones grow in length by an increase in the
cartilage, the cartilage gradually becoming ossified. Growth in diameter is accomplished
by the constant deposition of new layers of bone beneath the periosteum. During this
process the osteoclasts absorb the bone from within. The formation of the marrow cavity
is thus effected.

Classification of Bones.—The bones of the fowl are classified as long, short, flat, and
irregular.
Long Bones.—The long bones occur in the legs and wings, where they serve as levers
to sustain weight and make locomotion possible. A long bone consists of a shaft and two

extremities. The superior is called the proximal and the inferior the distal extremity. The
expanded articular surfaces in forming joints with adjoining bones afford ample space for
the attachment of ligaments. The shaft is cylindrical and hollow.
Short Bones.—Short bones occur in the feet and in the wings. Their structure is similar
to that of the long bones.
Flat Bones.—The flat bones occur where extensive protection is needed, as in the
cranial region; or where large surface for muscular attachments is needed, as in the costal
and pelvic regions. Flat bones are made up of two thin layers of compact bone with a
variable amount of cancellous tissue interposed.
Irregular Bones.—The irregular bones include the vertebræ, the patellæ, and the carpal
bones.

Composition of Bone.—Bone consists of organic and inorganic matter. Organic matter
gives toughness and elasticity to the bone, and inorganic matter hardness. The organic
substance of bone is called ossein. When boiled in water ossein is resolved into gelatin.
The following tables[1] give the results of an analysis of the femur, fresh, of a mature hen.
1. Grateful acknowledgment is hereby made to Dan M. McCarty, Chemist, Animal Industry Division, North
Carolina Agricultural Experiment Station, for this analysis.

Fresh femur:
Water 18.23 per cent.
Dry matter 81.77 per cent.
Dry matter:
Organic matter 63.09 parts
Inorganic matter 18.68 parts
Salts in dry matter:
Calcium 6.970 per cent.
Magnesium 0.283 per cent.
Potassium 0.004 per cent.
Sodium 0.276 per cent.
Iron 0.020 per cent.
Phosphorus 3.210 per cent.
Sulphur 0.085 per cent.
Chlorine 0.520 per cent.
Carbon dioxid 0.550 per cent.

The inorganic matter of the femur of the hen consists of 18.68 parts or 22.84 per cent.
of dry matter, and the organic matter of 77.16 per cent. Stated in other words the femur,
including its contained marrow, consists of organic and inorganic matter in the ratio of 3.4,
approximately, to 1.

The Skeleton of the Fowl.—The skeleton of a bird is remarkable for the rapidity of its
ossification. It is worthy of note that other parts of the bodies of adult birds also become

ossified. Among such parts are the tendons of the muscles of the legs, of the feet, and of
the neck; the plates of the corneal margin of the sclerotic tunic of the eye; and the stapes
of the ear. Ossification in birds at the attachments of the semi-lunar valves of the aorta and
of the pulmonary artery has been reported by Owen.
The bony structure is compact, and the bones contain a greater proportion of phosphate
of lime than do the osseous structures of mammals. Especially is this the case in those
parts of the skeleton which are permeated by air.

The Divisions of the Skeleton

( The Skull ( Cranium

( ( Face

The Axial skeleton ( ( Cervical region

( ( Dorsal region ( Ribs

( The Vertebral column ( ( Sternum

( Lumbar region

( Sacral region

( Coccygeal region

( Scapula

( Shoulder girdle ( Coracoid

( ( Clavicle

(

( ( Arm ( Humerus

( (

( Fore limb ( Forearm ( Radius

( ( ( Ulna

( (

( ( ( Carpus

The Appendicular skeleton ( ( Hand ( Metacarpus

( ( Phalanges

(

( Pelvic girdle ( Ilium

( (Hip bone) ( Ischium

( ( Pubis

(

( ( Thigh ( Femur

( Hind limb (

( Leg ( Tibia

( ( Fibula

(

( Foot ( Metatarsus

( Phalanges

The bodies of birds contain many air reservoirs to make them light that flying may be
more easy. Many bones have their weight in proportion to size and strength thus greatly
reduced. In very young birds the cavities of bones contain, instead of air spaces, loosely
arranged red marrow, which is in most bones later absorbed. The air reservoirs in bones
are most capacious in the best flyers. In the non-flyers more of the bones retain their red
marrow.
The bones supplied with air spaces are relatively larger than in mammals, and are
provided with small transverse osseous columns which cross in different directions and
from side to side. These cross beams give stability to the thin wall of the bone. The
membranes lining these cavities are very vascular.

The Axial Skeleton

THE SKULL

The skull is divided into the cranial and facial portions. In these parts we find present
31 bones: one occipital, two parietal, two frontal, one ethmoid, one sphenoid, and two
temporal; all of which constitute the cranial group; two premaxillary, two maxillæ, two
nasal, two lacrimal, two palatine, two pterygoid, two zygomatic, one vomeral, the two
jugal, and two quadrato-jugal, which constitute the facial group; two quadrati and one
inferior maxillary, which constitute the inferior jaw group.
The peculiarities of the skull are the long os incisivum and the single condyle located
on the occipital bone just below the foramen magnum. The condyle articulates with the
atlas.
The head of the bird is small in proportion to the size of the body, and in front it is
conical in shape.

The Cranium

The cranial cavity, or cavum cranii, incloses the brain with its membranes and vessels.
The dorsal wall, or roof, is formed by the frontal and the parietal bones. In the median
line of the cerebral portion is the internal parietal crest. The roof of the cerebellar portion
is marked centrally by a groove.
The posterior wall of the cerebellum is formed by the occipital bone.
The lateral wall is formed chiefly by the temporal bone. It is marked by a ridge which
divides the cavity into the cerebral and cerebellar compartments. The cerebral portion is
marked by a depression which receives the optic lobes. A crest divides this cavity from the
optic portion. The walls are marked by digitations and vascular grooves.

Fig. 4.—The skeleton of the domestic fowl. 1,
Os incisivum. 2, External nasal opening. 3, Os
nasale. 4, Os lachrymale. 5, Lamina
perpendicularis. 6, Os dentale. 7, Os palatine. 8,
Os quadrato-jugal. 9. Os pterygoideum. 10, Os
quadratum. 11, Os articulare. 12, External
auditory canal. 13, Atlas. 14, Os carpi radiale.
15, Radius. 16, First finger. 17, Os metacarpus.
18, Second finger. 19, Third finger. 20, Os carpi
ulnare. 21, Ulna. 22, Humerus. 23, Thoracic
vertebræ. 24, Scapula. 25, Os ilium. 26,
Foramen ischiadicum. 27, Caudal vertebræ. 28,
Pygostyle. 29, Foramen obturatum. 30, Os
ischium. 31, Processus uncinatus. 32, Vertebral
rib. 33, Os claviculum or furculum. 34, Os
coracoideum. 35, Os femoris. 36, Os pubis. 37,
Body of sternum. 38, Lateral internal process of
sternum. 39, Costal process of sternum. 40,
Sternal crest, cristi sterni, or keel of breast-
bone. 41, Sternal rib. 42, Lateral external
process of sternum. 43, Os fibula. 44, Xyphoid
process of sternum. 45, Internal notch. 46, Os
patella. 47, Os tibia. 48, Os metatarsus. 49,
Second toe. 50, Fourth toe. 51, Os metatarsale.
52, First toe. 53, Second toe. 54, Second
phalanx of second finger. 55, Os metacarpus.
56, Air opening in humerus. 57, Hypocledium.
58, External notch. 59, Cervical vertebræ. 60,
Foramen oblongum.

The ventral wall, floor, or basis cranii interna, may be regarded as forming five fossæ.
These are: one anterior, one middle, one posterior, and two lateral. The anterior fossa

supports the frontal and olfactory parts of the cerebrum. It lies at a higher level than the
middle fossa. The middle fossa, or fossa cranii media, is circular in outline and extends
into the lateral fossæ which lodge the olfactory lobes. Just back of the middle fossa is the
sulla turcica, upon which rests the pituitary body. The posterior fossa, or fossa cranii
posterior, lodges the medulla oblongata.

Bones of the Cranium (Figs. 4, 6, 7, and 8).—The bones of the cranium fuse early in
the chick’s life. The sutures uniting the bones can usually be seen in the fetus or in the
baby chick soon after it emerges from the shell. The major portion of the cranial bones
become entirely fused. Each cranial and each facial bone ossifies from a distinct center or
centers.
The cavity for the cerebrum is much larger than the cavity for the cerebellum. The
cranial cavities in birds are relatively larger than in mammals. The bones are designated as
in mammals. There are three single bones, the occipital, the ethmoid, and the sphenoid.
Those in pairs are the frontal, the parietal, and the temporal.

The Occipital. Location.—The occipital bone or os occipitale, is situated at the
posterior part of the cranium, of which it forms the posterior wall. This part is called the
base of the cranium. The occipital bone articulates with or touches inferiorly, the
sphenoid, laterally, the temporal, and superiorly, the parietal.
Development.—The occipital bone is developed from four centers of ossification; the
dorsal, or os occipitale superius, two lateral, or ossa occipitales laterales, and the ventral,
or os occipitale inferius, all of which may be seen distinct in the baby chick (Fig. 5, Part
II, No. 1).

Fig. 5.—Bones of the head and vertebra.

Part I.—1, The cranium. 2, The skull cap. 3,
The ethmoid bone. 4, The inferior maxilla. 5,
The palatine bone. 6, The quadrato-jugal. 7, The
jugal. 8, The superior maxilla. 9, The
premaxilla. 10, The horny covering for the
premaxilla. 11, The horny covering for the os
dentale. 12, The os quadratum. 13, The nasal
bone. 14, The pterygoid.

Part II.—1, The os occipitale (1, dorsal; 2, two
lateral; 3, ventral portions and 4, foramen
magnum). 2, The fourteen cervical vertebræ. (1,
atlas; 2, axis). 3, The seven dorsal vertebræ. 4,
The fourteen lumbo-sacral vertebræ. 5, The
seven coccygeal vertebræ. 6, The pelvis (1,
ilium; 2, ischium; 3, pubis; 4, cotyloid cavity or
acetabulum). 7, The vertebral column complete
from the baby chick. 8, The parietal bone. 9,
The temporal bone. 10, The frontal bone.

Description.—In the center of the occipital bone is the foramen magnum. Through this
foramen the spinal cord extends into the cranial cavity and connects with the medulla
oblongata. The occipital bone has a single condyle, which is located just below the
foramen magnum and articulates with the atlas. At the base of the condyle a small
subcondyloid fossa receives the body of the atlas during extreme flexion of the head. In
the center of the lateral wing of the occipital bone there is a small foramen through which
passes the hypoglossal nerve. Somewhat laterally from this foramen there is an opening
through which the vagus, or pneumogastric nerve passes. Laterally from these is the
canalis caroticus et jugularis. Between the os occipitale superius, or dorsal portion, and
the ossa parietalia is a space to which ligaments are attached, called the fontanel.

Fig. 6.—View of the frontal region of the skull
of a hen. 1, Parietal. 2, Frontal. 3, Nasal. 4,
Premaxilla. 5, Temporal. 6, Inferior jaw. 7,
Jugal bone.

The Ethmoid. Location.—The ethmoid, or os ethmoidale, forms the anterior wall of
the cranium, and the orbital septum. It is related anteriorly with the vomeral, superiorly
with the nasal and frontal, posteriorly with the temporal, and inferiorly with the sphenoid,
and palatine.
Description.—The ethmoid consists of a perpendicular and a horizontal lamina. The
perpendicular lamina, located between the orbital cavities, is called the septum
interorbitale. On each side of the septum interorbitale and near the superior orbital roof
are two foramina for the passage of the olfactory nerves. In the horizontal plate, which
forms the anterior cranial wall, are located the optic foramina through which pass the
optic nerves.

Fig. 7.—Side view of the skull of a hen. 1, Lamina perpendicularis. 2, Foramen for the passage
of the nerve of smell. 3, Foramen for the passage of the optic nerve. 4, Nasal bone. 5, External
nasal opening. 6, Premaxilla. 7, Os dentale. 8, Superior maxilla. 9, Os jugal. 10, Os quadrato-
jugal. 11, Os quadratus. 12, Pterygoideus. 13, Os articulare. 14, Inferior maxilla. 15, Temporal.
16, External auditory canal. 17, Parietal. 18, Frontal. 19, Palatine. 20, Orbital process, posterior
to which is the processus zygomaticus. 21, Interorbital foramen and optic foramen for passage
of optic nerve. 22, Attachment for inferior oblique; 23, for superior oblique; 24, for levator
palpebræ superioris; 25, for internal rectus; 26, for superior rectus; 27, for external rectus; 28,
for inferior rectus; 28, for inferior rectus; 29, for depressor palpebræ inferioris; 30, for
orbicularis palpebrarum; 31, for tensor tympani; 32, for circumconcha.

The Sphenoid. Location.—The sphenoid, or os sphenoidale, forms the floor of the
cranial cavity and articulates with or touches posteriorly the occipital, laterally the
temporal, and anteriorly the palatine, and ethmoid.
Description.—The sphenoid bone, the largest part of the cranial floor, is formed by the
fusion of the nasal and the cranial parts. It is a three-cornered bone with two, thin, broad
wings. These wings are divided into two portions, orbital wings, or alæ orbitales, and
temporal wings, or alæ temporales. The temporal wing forms a cover for the Eustachian
tube trumpet, and for the canal coming from the sella turcica, which latter gives passage to
the intracranial carotid artery. The orbital wing forms the lower portion of the posterior
wall of the orbital cavity, and lies directly before the os petrosum or temporal bone where
the second and third branches of the fifth pair of cranial nerves emerge from the cranial
cavity.
Anteriorly the sphenoid has a foramen for the passage of the Eustachian tube, the tuba
auditiva, and also a sharp-pointed projection, the nasal portion, called the rostrum.

The Frontal. Location.—The frontal bones, or ossa frontales, two in number, form the
forehead, a portion of the nose, and a portion of the roof of the orbital cavities. They are
related posteriorly with the parietal, laterally with the temporal and zygomatic, and
anteriorly with the nasal and premaxillary. They touch inferiorly the ethmoid.

Description.—Each of these bones has a processus orbitalis which is seen at the outer
margin of the posterior and upper orbital wall and just in front of the zygomatic process of
the squamous portion of the temporal. The frontal bone forms the anterior portion of the
superior wall of the cranial cavity. The two bones are thin, flat, and meet at the median
line of the forehead. The external surface is convex. The inner surface has a ridge located
longitudinally and in the center the bone becomes narrow anteriorly.

The Parietal. Location.—The parietal bones, or ossa parietalia, two in number, form
the posterior part of the roof of the cranial cavity. They meet in the median line and are
related posteriorly with the occipital, anteriorly with the frontal, and laterally with the
temporal bones.
Description.—The parietal bones are short and very broad (Fig. 5, Part II, No. 8). Each
bone is quadrilateral in outline and has two surfaces, four borders and four angles. The
external parietal surface is convex and smooth and the internal, cerebral surface is
concave.

The Temporal. Location.—The temporal bones, or ossa temporales, two in number, are
located at the lateral portion of the cranium, and aid in the formation of the cranial wall.
The temporal bone is related posteriorly with the occipital, superiorly with the parietal and
frontal, externally with the quadratus, anteriorly with the ethmoid, and inferiorly with the
sphenoid.
Description.—The temporal bones consist of the fused squamous and petrous
temporals; they contain the essential organs of hearing.

Fig. 8.—Inferior view of the skull of a hen. 1,
Occipital. 2, Foramen magnum. 3, Occipital
condyle and just below the basi-occipital. 4,
Foramen for the passage of the hypoglossal
nerve. 5, Foramen for the passage of the vagus.
6, Canalis caroticus and jugulare. 7, Sphenoid.
8, Temporal wings of the sphenoid. 9, Foramen
auditiva. 10, Os articulare. 11, Os angulare. 12,
Vomer. 13, Os dentale. 14, Pterygoid.

The squamous portion of the temporal bone possesses the long thin zygomatic process
sometimes called the posterior orbitalis. It forms a small flattened tongue, directed
forward, sometimes free, and at other times united by its superior border to the summit of
the orbital process. This is especially true in the turkey. This process is seen near the lower
outer portion of the posterior orbital wall. The squamous portion is also provided antero-
laterally with an articular facet which articulates with the quadrate bone. The large portion
of the temporal bone lies on the side of the cranium superior to the ala sphenoida
temporale. It extends outward and anteriorly over the rims of the petrosum and ala
sphenoida orbitale. The squamous part forms the upper three-fourths of the cochlea, the
inner auditory canal, the upper part of the fenestra ovalis, the anterior vertical and the
outer semicircular canal, and the lower part of the posterior vertical semicircular canal.
The petrous portion forms the posterior wall of the foramen ovale and the fenestra
ovalis in which lies the columella. The fenestra ovalis and the fenestra rotunda are the
only two entrances into the labyrinth. In this region may be seen the fusion line between
the os petrosum and the os occipitale. Superiorly and posteriorly the petrous portion
touches the external parietalia and occipitalis; infero-laterally it unites with the basi-

sphenoid. The outer rim of the foramen ovale is broadened by the ala sphenoida and
mesially by the basi-sphenoid. This foramen gives exit to the second and third divisions of
the fifth pair of cranial nerves.
The lateral surface of the temporal bone presents a short tube, the external acoustic
process, or processus acusticus externus, to which is attached the concha of the ear. The
process is directed outward. Its lumen, the external acoustic meatus, or meatus acusticus
externus, conducts to the cavity of the middle ear in the bare skull, but is separated from it
by the tympanic membrane in the natural state.

Bones of the Face

The bones of the face, or ossa faciei, are the premaxillary, or upper mandible, the
maxillæ, the nasal, the lacrimal, the palatine, the pterygoid, the zygomatic, the vomeral,
the jugal and the quadrato-jugal. The vomer is single, the others are paired. In the inferior
maxillary group there are the quadrati, and the inferior maxillary, or lower mandible. The
turbinated and hyoid bones are also discussed with the bones of the face.
The beak consists of the anterior portion of the upper and lower mandibles which are
covered with a horny structure.

The Premaxilla. Location.—The premaxillæ, or ossa incisiva, or mandibular
structures, are located in the extreme anterior facial region.
Description.—The premaxillæ are long and the anterior end is pointed. Each consist of
two lateral halves which become fused before the chick is hatched. They partly
circumscribe the openings into the nose. This bone is the base of the upper portion of the
beak and determines its form. It forms the anterior walls of the nasal cavity. It has between
the nasal bones, two processes which extend back to the anterior point of the cerebral
cavity. The posterior part of the incisivum and nasale are flat, thin, and elastic. The
extensions then are the processus maxillaris, the processus palatinus, and the processus
frontalis, the first of which forms part of the jaw rim, the second, which aids in forming
the gum plate, and the last which reaches to the anterior portion of the cranial wall.

The Maxilla. Location.—The superior maxillaries, or ossa maxillares, two in number,
form the floor of the upper beak, a part of the palatine roof and nasal walls.
Each maxilla borders laterally the premaxilla and the nasal; inferiorly, the anterior point
of the palatine; and posteriorly, the jugale.
Description.—The maxillæ are thin, flat, bones. They have three borders and three
angles. The palatine processes of the two bones do not meet in the median line, which
results in a cleft in the median palatine region. The bone-like gums are formed partly by
the palatine processes but more largely by lateral wings of the os incisivum. Each maxilla
has posteriorly a yoke-like extension, superiorly a small extension, and also a palatine
process. The latter articulates by a facet with the vomer.

The Nasal. Location.—The nasal bones, or ossa nasalia, two in number, are located in
the lateral facial region. The nasal bone articulates posteriorly with the frontal; laterally,
on the inner border, with the processus frontalis of the premaxilla, and on the outer border
with the lacrimal; and inferiorly with the premaxilla, maxilla, jugale, and vomer.
Description.—The nasal bone, or os nasale, is broad, flat, and elastic and forms the
posterior wall of the nasal opening. Under this bone is located the infraorbital sinus.
There are three extensions: first, the processus intermaxillaris, which forms the upper
wall of the nasal cavity; second, the processus maxillaris anterior, directed downward and
forward, which fuses with the maxillary bone and forms the posterior rim of the nasal
cavity; and third, a posterior processus frontalis, which lies parallel with the ethmoid.

The Lacrimal. Location.—The lacrimal bones, or ossa lacrimalia, two in number, are
located at the outer border and at the junction of the processus frontalis of the nasal, with
the frontal bone.
Description.—The lacrimal bone is small, and rather filiform. They become fused with
the nasal and the frontal bones, forming part of the margin of each.

The Palatine.—Location. The palatine bones, or ossa palatina, two in number, enter
into the formation of the inner part of the bony gum and hard palate, or roof of the mouth.
They form the support for the hard palate. Each palatine articulates posteriorly with the
rostrum, or nasal portion of the sphenoid, and with the pterygoid; and anteriorly with the
maxilla.
Description.—The palatine bone is curled posteriorly and is thin at the upper portion
and thick at the lower border. Anteriorly it has a long rather filiform projection.

The Pterygoid. Location.—The pterygoid bones, or ossa pterygoidea, two in number,
are located back of the region of the posterior nares. They extend diagonally outward and
backward from the median region of the sphenoid rostrum to the quadrate bone. They
articulate anteriorly with the sphenoid rostrum and the palatine, and posteriorly with the
quadrate.
Description.—The pterygoid bones are slender and cylindrical, and are expanded at the
ends into an articular facet.

The Zygomatic. Location.—The zygomatic, or ossa zygomatica, two in number are
situated below the orbital cavity and extend from the maxilla to the quadrate bone.
Description.—The zygomatic is small, slender, rod-shaped, and forms the lateral
portion of the upper jaw. The anterior portion of the zygomatic represents the jugal and is
fused with the maxilla and with the anterior processus maxillaris of the nasal bone, the
maxilla, and the posterior portion, the quadrato-jugal, which articulates with the quadrate
bone.

The Vomer. Location.—The vomer is located in the median nasal septum. It articulates
with the rostrum of the sphenoid, being connected to it by a mass of ligaments. It touches
anteriorly the posterior portion of the maxilla.
Description.—The vomer is a median bone and aids in the formation of the septum
nasi. It consists of a thin plate, thickest posteriorly and diminishing toward the anterior
edge.

The Jugal and Quadrato-jugal.—The jugal and quadrato-jugal are united forming a
long slender cylindrical bone called the zygomatic, lying at the outer side of the upper jaw.
They have been described under zygomatic, which see.

The Quadrate. Location.—The quadrate bones, or ossa quadrata, two in number, are
located antero-laterally to the temporal bones. Each articulates inferiorly with the posterior
articular portion, or pars articulare, of the inferior maxilla and infero-laterally with the
quadrato-jugalare portion of the zygomatic. It articulates antero-internally with the
pterygoid and supero-posteriorly with the temporal.
Description.—The quadrate bone is anvil-like in shape. It has an anterior process, the
orbital process, for muscular attachments, and posteriorly it affords attachment to the ear
drum.

The Inferior Maxilla. Location.—The inferior maxilla, lower jaw, or os maxillare
inferius, also called the mandibular bone, or pars dentis, is analogous to the lower jaw of
mammals. It articulates posteriorly with the quadrate bone.
Description.—The inferior maxilla is the largest bone of the face. It is made up of a
right and a left limb which are separate in the fetus and which unite subsequently
anteriorly, forming the inferior portion of the beak. Each limb of the jaw is developed
from five elements: the pars articularis, which forms the jaw-joint and, expanded,
articulates with the quadrate bone; the pars angularis, lying just in front of the pars
articularis; the pars supra-angularis, a slender bone lying just above the angularis; the
splenial, a thin plate of bone, lying along the inner surface of the mandible; and the pars
dentalis, which forms the anterior portion of the jaw.

The Turbinate Bones. Location.—The turbinate bones, or ossa turbinata, six in
number, are attached to the lateral walls of the nasal cavity (Fig. 26, No. A, 1 and 2). In
each nasal cavity there are three turbinate bones, one anterior and two posterior. Of the
two posterior the upper one lies supero-posterior to the inferior one. The turbinate bones
are attached to the lateral nasal walls, project into the cavity and thus greatly diminishing
its extent.
Description.—Each turbinate bone is composed of a very thin lamina, finely cribriform
in many places, and in the fresh state, covered on both sides with mucous membrane.

These bones are curled and partly membrano-cartilaginous structures which give greater
surface in the nasal passage for mucous membrane in which the olfactory nerve terminal
filaments are distributed.

The Nasal Cavity.—The nasal cavity, or cavum nasi, is a longitudinal passage which
extends through the upper part of the face. It is divided into right and left halves by a
median septum nasi. Its walls are made up of the premaxilla, maxilla, nasal, vomer, and
palatine bones.

The Hyoid Bone. Location.—The hyoid bone, or os hyoideum, is situated chiefly
between the rami of the mandible, but its upper part extends around the outer margin of
the base of the skull. The hyoid bone does not articulate with any bones of the skull, but is
firmly attached by strong fibrous structure.
Description.—The hyoid bone consists of the following parts: the body, or basi-hyal,
which is subcylindrical and presents in front a trochlear articular surface, convex
transversely, and concave vertically for articulation with the ewer-shaped portion of the
glosso-hyal. The anterior free portion, or lingual process, is called the glosso-hyal, or
entoglossal bone. The lingual process gives support to the muscular and fibrous structures
of the tongue. On either side of the basi-hyal there is a limb passing posteriorly along the
side of the superior larynx, extending upward along the outer border of the occipital bone.
This is the cornu of the os hyoideum and is divided into two elements, first, the basi-
branchial which is bone and articulates with the basi-hyal, and the second, the cerato-
branchial, cartilaginous in structure. In the center and projecting backward from the body
of the os hyoideum is a spur process called the uro-hyal, partly bony and partly
cartilaginous, and which rests upon the superior larynx.

THE VERTEBRAL COLUMN

The vertebral, or spinal column consists of 42 bones, as shown in the following table:

Cervical region 14
Dorsal region 7
Lumbo-sacral region 14
Coccygeal region 7

Total 42

Many of the bones of the dorsal and lumbo-sacral regions do not have free articulations.
The cervical and coccygeal alone have free movements.

The Cervical Vertebræ (Fig. 4, No. 59; Fig. 5, Part II, No. 2). Location.—The cervical
vertebræ form the neck of the fowl.

Fig. 9.—Os hyoidum and tongue muscles. 1,
Glosso-hyal. 3, Basi-hyal. 4, Basi-branchial
element of the cornua. 5, Cerato-branchial
element of the cornua. 6, Uro-hyal or spur
process. 7, Genio-hyoideus. 8, Cerato-hyoideus
showing the slender tendon. 9, Hyoideus
transversus. 10, Hyoideus transversus.

Description.—The long cervical section of the spinal column is S-shaped and is made
up of fourteen vertebræ. The anterior segments move freely forward, the middle ones
backward and the posterior ones forward, allowing the S-shaped curve of the neck. The
neck is flexible so that it is possible for the beak to reach the coccygeal oil gland. The bird
is enabled to reach the feathers on all parts of the body to cleanse and oil them.

The Atlas. Location.—The first cervical vertebra is called the atlas. Anteriorly it
articulates with the single condyle of the occipital bone. Posteriorly it articulates with the
axis, or second cervical vertebra.
Description.—The atlas is the smallest of the cervical vertebræ and is ring-shaped. The
anterior articular surface, half-moon in shape, forms a deep articular cavity. The joint,
called a ball-and-socket joint, makes possible movements in all directions. The condyle of
the occiput also touches an articular end of the odontoid process of the axis, or second

cervical vertebra. Posteriorly there projects from the atlas two small lateral wings
possessing articular facets which articulate with similar facets on the lateral wings of the
axis. Posteriorly the body of the atlas is also provided with an articular surface which
articulates with a similar surface on the anterior portion of the body of the axis.

The Axis. Location.—The axis is the second cervical vertebra. It articulates anteriorly
with the atlas, and by a facet on the extreme anterior end of the odontoid process, with the
condyle of the occipital bone. Posteriorly it articulates with the third cervical vertebra.
Description.—The body of the axis is short. The upper anterior portion of the body of
the axis is provided with a tooth-like process called the odontoid process. There are two
anterior lateral wings provided with small articular facets which articulate with similar
facets of the atlas. The anterior surface of the body of the axis forms a true articulation
with the body of the atlas.
The axis is provided with a superior and an inferior spine. There are two posterior
articular processes which articulate with the prezygapophyses, or anterior articular
processes, of the third cervical vertebra. The posterior part of the body of the axis forms a
true articulation with the body of the third cervical vertebra.

Other Cervical Vertebræ.—Beginning with the axis, the body of which is relatively
short, the body of each succeeding vertebra is longer than that of the preceding. The
articulations of each vertebra with adjoining vertebræ are effected by means of
diarthrodial facets, convex in one direction and concave in the other.

Fig. 10.—A. Diagram of three first dorsal
vertebræ and scapular arch-side view. B.
Diagram of section through the hemal arch.

A. 1, First dorsal segment. 2, Second. 3, Third. 4
and 5, Hemal arches. 6, The pleurapophyses or
floating ribs. 7, The third pleurapophyses or
dorsal vertebral rib articulating with the
hemapophysis or sternal rib, 8, and this in turn
with the wing of the sternum form a hemal arch.
9, The sternum. 10, Intervertebral foramen
through which the nerves pass. 11, Articulation
with the body of vertebra parapophyses. 12,
Articulation with transverse process or
diapophyses. 13, Oblique process or
zygapophysis. 14, The epipleural appendage.

B. 1, Hemal or inferior spine (hypapophysis). 2,
The neural arch. 3, The pleurapophyses or rib.
4, The superior or neural spine or neurapophysis
which aids in the formation of the anapophyseal
ridge. 5, Parapophyseal surface for head of rib.
6, Tubercle of rib articulating with the
diapophysis. 7, Lamina of neurapophysis. 8,
Centrum. 9, Hemal arch.

Between the bodies of the vertebræ are pads of fibrous cartilage. Above these bodies
and inferior to the neural spines extends throughout the spinal column the large neural
canal which is occupied by the spinal cord. Between the vertebral segments the neural

canal is exposed superiorly, since here the neural arches do not completely bridge the
canal. These spaces are protected by intervertebral ligaments.
In addition to the superior neural spines and the inferior spines, from the body of the
vertebra project lateral processes, and anterior and posterior oblique processes.
All cervical vertebræ except the atlas and the axis are made up of the following parts: a
body, or centrum, a neural canal, a neural arch, a superior dorsal, or neural spine, or
neurapophysis, which in most cervical vertebræ is only slightly developed, two oblique
processes, or zygapophyses, two transverse processes, or diapophyses (Fig. 10, No. 12)
and in some vertebræ two tubercles, or anapophyses above the posterior zygapophyses.
The prezygapophyses are directed upward and inward; the postzygapophyses are directed
downward and outward. The inferior spines are only well developed in the last two or
three cervical vertebræ.
Between vertebral segments, except the central sacral portion, on each side, there is an
intervertebral foramen (Fig. 11, No. A, 4), through which pass the spinal nerves. In the
central portion of the sacrum where the vertebræ have fused, there are two foramina on
each side for each original vertebra, one located above the other, the upper giving passage
to the sensory branch, the lower to the motor branch of the nerve.
The Dorsal Vertebræ (Fig. 4, No. 23; Fig. 11, A). Location.—The dorsal, or thoracic
vertebræ, or vertebræ thoracicales, aid in forming the roof of the chest cavity.
Description.—The dorsal vertebral section is made up of seven vertebræ, with strong
short bodies. The first and sixth dorsal segments articulate as do the cervical, by the bodies
and oblique processes. (Fig. 11, No. A, 3, illustrates the oblique processes.) The seventh
dorsal is fused with the first lumbo-sacral vertebra. The second to the fifth inclusive of the
vertebræ are fused together, and the superior and inferior spinous processes are fused into
a prominent plate-like ridge.
The transverse processes of the dorsal vertebræ, from the second to the sixth, are well
developed and are bridged over with a thin layer of bone. The ventral spines are partly
fused and form a very prominent and continuous ridge. (Fig. 11, No. A, 1, shows the fused
superior spines; No. 2, the fused inferior spines; and No. 4, the intervertebral foramina.)
The Lumbo-sacral Vertebræ (Fig. 5, Part II, No. 4). Location.—The fused lumbo-
sacral section of the spinal column forms the roof of the pelvic cavity.

Fig. 11.—Bones from the scapular arch.

A. Dorsal vertebra. 1, Superior spinous ridge, 2,
Inferior spinous ridge. 3, Oblique processes. 4,
Intervertebral foramina. 5, Articular facette for
head of the rib. 6, Articular facette for tubercle
of the rib. 7, Articular portion of the body.

B. Outer surface of scapula.

C. Inner surface of scapula. 1, Thin caudal end.
2, Articular head. 4, Processus furcularis. 5,
Processus humeralis. 6, Processus coracoideus.

D. Outer surface of coracoid.

E. Inner surface of coracoid. 1, The furcular
tuberosity. 2, Articular facette for articulation
with the sternum. 3, Articular surface for
humerus and scapula.

F. Outer surface of humerus and G the inner
surface of the same. 1, Trochanteric fossa. 2,
Oval articular head at proximal end. 3, Shaft. 4,
Distal end showing articular condyles. 5,
Trochanter. 6, Trochlea for ulna. 7, Trochlea for
radius. 8, Depression or fossa.

H. Section through the median plane of the
humerus showing the delicate cross partitions
illustrating provisions made for bones provided
with air-sac extensions.

Description.—The lumbo-sacral region consists of fourteen vertebræ which are distinct
in the body of the newly hatched chick, but which become fused soon after hatching. With
these vertebral segments there are fused the last dorsal and first coccygeal vertebral
segments. This fusion is so complete that the segments are indicated only by the
intervertebral foramina on the sides through which the spinal nerves pass, and by
transverse markings on the inferior surface of the bodies.
The lumbo-sacral vertebræ, called the sacrum, and the ilia are fused. The dorsal spines
of the vertebral segments are indicated only in the anterior portion where they are fused,
forming a plate. There are no prominent ventral spines.
The Coccygeal Vertebræ (Fig. 4, No. 27). Location.—The coccygeal or caudal
vertebræ, or vertebræ coccygeæ, constitute the bones of the tail.
Description.—There are seven coccygeal vertebræ. The last segment, shaped like a
plough share and therefore called the pygostyle, is the largest and is supposed to have
been formed by the fusion of several original distinct segments. It supports the coccygeal
oil gland and the row of rudder feathers, or rectrices, which are arranged fan-wise.
All of the coccygeal vertebræ except the first are freely movable, thus allowing the tail
to be used as a rudder during flight. The lateral spines are long and well developed, and
the superior spines are bifurcated, thus giving increased surface for muscular attachment.
The first coccygeal segment is fused with the last lumbo-sacral vertebra.

THE THORAX

The dorsal vertebræ superiorly, the ribs laterally, and the sternum, or breast-bone
inferiorly, form the skeleton of a large cavity called the thorax. The dorsal vertebræ have
been described.
The Ribs (Fig. 4, No. 32; Fig. 10, A and B). Location.—The ribs form the lateral bony
wall of the thorax, articulating superiorly with the dorsal vertebræ.
Description.—The ribs are arranged in order of length, the ultimate rib being the
longest. From anterior to posterior, they approach more nearly a horizontal position. The
ribs are divided into the true and the false. The true ribs articulate with the sternum. The
false ribs do not touch the sternum; they are floating. The true ribs are composed of two
parts, a vertebral, or dorsal, and a sternal, or ventral. The vertebral part, or extremitas
vertebralis, is provided with an articular head, or caput costæ; a neck, or collum costæ;
and an articular tubercle, or tuberculum costæ. The head and tubercle articulate with the
dorsal vertebra. Below the head of each rib is a pneumatic foramen.
The distal extremity of the dorsal section of the rib articulates with the proximal end of
the sternal section by a diarthrodial articulation.
The articulations of the true ribs with the sternum is diarthrodial and each articulate by
two small ridges with a double sternal facet. The first, the second, and the seventh ribs are
floating, or false ribs. The first rib articulates with the quadrate part of the last cervical
vertebra and also with the first dorsal vertebra. The seventh, the last rib, articulates with

the under side of the anterior alar part of the ilium. This rib is situated similarly to the true
ribs; but, instead of articulating directly with the sternum, the lower end lies against the
sternal segment of the rib just anterior to it.
From the posterior edge of the second, the third, the fourth, and the fifth ribs, and near
the middle of the dorsal segment, are flat, uncinate, bony processes which project upward
and backward, overlying in each case, the succeeding rib and giving greater surface for
muscular attachments and greater stability to the thorax.
The Sternum (Fig. 4, No. 40; Fig. 10, No. A, 9). Location.—The sternum, or breast-
bone forms the inferior portion, or floor of the thoracic cavity.
Description.—The sternum is a quadrilateral, curved plate with processes projecting
from each angle and from the middle of the anterior and posterior borders. The posterior
medial projection, or metasternum, is the longest, and has a tall, plate-like ridge—the
sternal crest, crista sterni—running along its ventral surface. The crest serves the
important function of increasing the bony area for the attachment of the powerful muscles
which move the wings. The anterior medial projection, or rostrum, is short, and pierced at
its root by an opening from which extend two elongated, saddle-shaped depressions into
which the end of the coracoid bones are received.
The plate-like process of bone, the posterior lateral process, which projects from the
caudal angles of the sternum soon divides into two parts. The shorter of these, the oblique
process, broadens toward its free end and covers the sternal segments of the last two ribs.
The sides of the sternum are thus provided with an external and an internal process
forming an external and an internal notch. These notches are bridged over by a broad
ligament, to which the muscles are attached. In poor flyers, as the domestic fowl, these
notches are large. The posterior end of the sternum is called the xiphoid process or
processus xiphoideus. Anteriorly the sternum is provided with lateral external processes,
the costal processes. The lateral borders of the sternum are pitted by four depressions into
which the sternal segments of the ribs are received. The dorsal, or inner surface of the
bone is pierced by openings by which the air-sacs communicate with the interior.

The Appendicular Skeleton

The appendicular skeleton consists of the shoulder girdle, the fore limb, the pelvic
girdle, or hip bone, and the hind limb. The shoulder girdle consists of the scapula, the
coracoid, and the clavicle. The fore limb consists of the arm, forearm, and the hand. The
arm consists of the humerus, the forearm of the radius and the ulna; and the hand consists
of the carpus, the metacarpus, and the phalanges. The pelvic girdle consists of the ilium,
the ischium, and the pubis. The hind limb consists of the thigh, the leg, and the foot. The
thigh consists of the femur, and the leg consists of the tibia and the fibula. The foot
consists of the metatarsus and the phalanges.

THE SHOULDER GIRDLE

The shoulder girdle consists of the scapula, the clavicle and the coracoid.
The Scapula. Location.—The scapula (Fig. 11, A, B) lies on the outer and superior rib
surface, extending parallel with the dorsal vertebræ.
Description.—The scapula is a thin, sword-like bone, becoming thicker as it approaches
the shoulder-joint. The scapula expands and becomes thin near the free end, which reaches
nearly to the antero-lateral portion of the ilium (Fig. 4, No. 24). The scapula articulates
with the coracoid. A pneumatic foramen is located at the base of the acromion process.
The anterior part of the scapula is provided with an articular head and is provided with an
inner process, called the processus furcularis, which lies near the furcula and coracoid. An
outer stronger processus humeralis forms the posterior half of the glenoid cavity, or
cavitas glenoidalis, in which the humerus articulates and the processus coracoideus.
The Clavicle. Location.—The clavicles, commonly known as the wish bone, are
located in the anterior chest region.
Description.—The clavicles are long, slender bones uniting below in the hypocledium, a
laterally flattened process. They are joined to the upper end of the coracoid by fibrous
cartilage. The hypocledium is joined to the anterior point of the sternum by the
claviculosternal ligament. The clavicles, as united by the hypocledium, form a v-shaped
structure called the furculum, or, popularly, the wish bone.
The forks play the part of an elastic spring, whose office it is to prevent the wings from
coming toward each other during contraction of the depressor muscles. The conformation
of this bone is, therefore, like the sternum, related to the extent and power of flight; and
for this reason it is that, in swift flyers, the two branches of the furculum are thick, solid,
widely separated, and curved like a U; while in those that fly heavily and with difficulty,
these branches are thin and weak, and join at an acute angle. The latter formation greatly
diminishes its strength, and lessens, in a singular manner, the reactionary power of the
bony arch it represents.

The Coracoid. Location.—The coracoid is located just back of the clavicle and at the
side of the entrance of the thoracic cavity. It is the strongest bone of the shoulder girdle,
extending upward, outward, and forward. It articulates inferiorly with the sternum and
superiorly with the humerus and the scapula, and is attached to the superior end of the
furcular limb by a fibrous cartilage.
Description.—It is thinnest in the center or shaft and broadens toward the inferior
extremity. The upper hook-like part of the coracoid forms the fore part of the glenoid
cavity, and together with the scapula and furcula form the foramen triosseum through
which passes the tendon of the elevator muscle of the wing. The upper end flattens out
into three tuberosities, the tuberositas furcularis which is thick and to which attaches the
limb of the furcula, the tuberositas scapularis which unites to the scapula, and the
tuberositas humeralis which lies between these and articulates with the humerus.

THE FORE LIMB

The bones of the fore limb are humerus, ulna, radius, carpus, metacarpus, and
phalanges.
The Humerus. Location.—The humerus constitutes the arm, which, when at rest, lies
parallel to the dorsal vertebræ. It articulates superiorly with the glenoid cavity, a shallow
ball-and-socket joint, formed by the scapula and the coracoid; and inferiorly with the ulna
and radius.
Description.—The proximal extremity of the humerus is provided with a trochanter
(Fig. 11, G, No. 5) and a large oval head or caput humeri, which articulates in the glenoid
cavity. The head is an elongate, semi-oval convexity, with the long axis transverse from
the radial to the ulnar side and with the ends continued into upper and lower crests. The
upper crest of the head of the humerus is on the radial side and the lower crest on the
under side. Under this latter crest there is a pneumatic fossa (Fig. 11, F, No. 1), at the
upper end of which there is an opening into the bone, the pneumatic foramen, which
brings the air-sac into communication with the air space of the bone. The shaft, or corpus
humeris, is irregularly cylindrical and slightly S-shaped.
The proximal part of the shaft, which is expanded on the palmar side, is concave across
and convex lengthwise. The distal part is slightly flattened. The shaft of the humerus is
almost cylindrical.
The distal extremity of the humerus is provided with two articular condyles, one of
which articulates with the ulna and the other with the radius. On the radial side of the
palmar surface there is a ridge; and on the ulnar side of the same surface there is a second
ridge diverging to the opposite tuberosity. The radial surface is a narrow, subelongate
convexity, extending from the middle, approximately, of the palmar surface, obliquely to
the lower part of the radial tuberosity. The two articular convexities, or trochlea, at the
distal end of the humerus are bent toward the palmar aspect, the anconal aspect is the side
on which the elbow is situated. The inner convexity is the larger and articulates with the
ulna. To the outside is the processus cubitalis humeri. The outer articulates with the radius

and is so arranged that the radius makes a greater flexion than the ulna. At the lower end
of the humerus there is a depression which receives the anconeus of the ulna during
flexion and extension of the forearm. On the shoulder- and elbow-joint are found grooves
over which the tendons glide, at which places sheaths are provided. This arrangement also
aids in keeping the capsular ligament in place.
The Ulna. Location.—The ulna, larger than the radius, is bent and articulates with the
radius only at the ends. The two bones are bound together by a ligamentous band. It also
articulates superiorly with the distal end of the humerus, and inferiorly with the carpus.
When the wing is folded the radius is superior and a trifle to the inner side of the ulna.
Description.—The proximal end is most expanded, and is obliquely truncate for the
articular excavation adapted to the ulnar tubercle of the humerus. A short angular process
behind the cavity represents the olecranon, which is the processus olecranalis
coracoideus ulnæ to which the ligamentum capsulare cubiti attaches. On the inner side of
the head is the internal tubercle of the ulna and on the external side the external tubercle of
the ulna. An excavation is noted on the radial side of the proximal end for the lateral
articulation of the head of the radius. On the upper side near the articular part is located
the sigmoid cavity.
The shaft, or corpus ulnæ, decreases in size near the distal end. It is slightly curved,
flattened laterally with an internal and an external ridge.
The distal end of the ulna is slightly expanded into a trochlea which is sharply convex
and articulates with two free carpal bones, the scapho-lunar, or os carpi radiale, and the
cuneiform, or os carpi ulnare. The scapho-lunar is placed on the radial side, and the
carpiulnare on the ulnar side. The distal extremity of the ulna is provided with a styloid
process and on the dorsal side with a tubercle.
The Radius. Location.—The radius lies beside the ulna with which it articulates at each
extremity. At the inferior extremity the articulation is rotary. It also articulates superiorly
with the humerus and inferiorly with the os carpi radiale.
Description.—The radius, cylindrical in shape, is more slender than the ulna.
The proximal end is expanded, subelliptical, with a concavity for the oblique tubercle
and a thickened convex border for articulation with the ulna. This end is provided with the
tuberositas radii.
The shaft, or corpus radii, is slender, subcompressed, and has a slight bend upward from
the ulna. A nutrient foramen occurs in this shaft.
The distal end is expanded and rather flattened with two grooves on the anconal side for
passage of tendons. For articulation with the scapho-lunar the radius is provided with a
terminal transverse convexity produced palmad, which also articulates with the ulna
laterally. There is a tuberosity on the radial side of the expansion and inferiorly the
inferior tuberculum ossis carpi radialis and superiorly a superior tuberculum ossis carpi
radialis.
The Hand.—The hand is made up of the carpus, the metacarpus, and the phalanges.
The bones of the hand are so arranged as to allow abduction and adduction, or flexion
in the ulno-radial plane, movements which are necessary in the outspreading and folding

of the wing. Thus the hand of the fowl moves in a state of pronation, without the power of
rotation. The carpal bones are so placed between the anterior arm and metacarpus as to
reduce the abduction which is necessary to hold and extend the wing, so that the hand or
wing be in a fixed position.
The Carpus.—The carpus in the domestic fowl is represented by two bones, ossa carpi,
called the scapho-lunar, or os carpi radiale, and the cuneiform, or os carpi ulnare. The
scapho-lunar is the smaller and is located between the radius and metacarpus. The
cuneiform is the larger and is located between the ulna, the radius, and the metacarpus.
The cuneiform is somewhat anvil-like in shape, being provided with a body and two
prongs.
The Metacarpus.—The metacarpal bones, or ossa metacarpi, two in number, are
separated at their middle portion, and consolidated at their extremities. The upper
proximal base of the metacarpus is provided with a tubercle, the tuberculum muscularis,
and externally the tuberculum ulnare ossis metacarpi. The distal end of the metacarpal
bone is provided with a tuberculum articulare.
The Phalanges.—The first three fingers only are represented, and these are
rudimentary.
The first finger called the pollex or thumb, consists of but one joint. It is located on the
proximal and outer end of the metacarpal bone. It has on its proximal end a tubercle, the
tuberculum articulare.
The second finger, the best developed, consists of two phalanxes. These are the main
bones extending from the metacarpus. Each articular end is provided with a tuberculum
articulare.
The third finger, small, cylindrical in shape, is located at the distal and inner side of the
metacarpal bone.

THE PELVIC GIRDLE (Fig. 4, No. 25; Fig. 5, Part II, 6)
The pelvic girdle is made up of three bones as follows: the ilium, the ischium, and the
pubis, all of which are fused in adult life. They are separate in the baby chick (Fig. 5, Part
II, 6). The pelvis together with the lumbo-sacral vertebræ forms a thin, irregular, shell-like
structure extending superiorly from the tail to the thoracic region. The sacrum is broad
posteriorly and together with the ilium forms the pelvic roof. The ilium and ischium are its
lateral walls.
The top surface of the pelvis shows the fovea ilio-lumbalis dorsalis, which is bounded
mesially by the crista ilii. Between it and the spina lumbalis there is a broad furrow, the
bottom of which is formed by the dorsal surface of the lumbar vertebræ. The sulcus ilio-
lumbalis dorsalis is formed by the rims of the ilia, so that a ridge is observable. The
cavum ilio-lumbale dorsale is formed by the iliac rims on either side. Anteriorly is the
canalis ilio-lumbalis, which is formed by the ilium and the lumbar vertebral spines. It is
located longitudinally to the vertebræ. The anterior opening of this canal is the larger.
Posterior to the acetabulum is the post-acetabular ridge.

The under part of the pelvis presents three distinct regions. The cavity is divided into
the fovea lumbalis, or anterior part, the fovea ischiadica, or mesial part, and the fovea
pudendalis, or posterior part. Posterior to these is the region called the planum coccygeum.
The fovea lumbalis contains the anterior lobe of the kidney, and is circumscribed
anteriorly by the last rib-carrying vertebra, and posteriorly by the transverse process of the
last lumbar vertebra.
In the fovea ischiadica which follows, lie the nerve plexus ischiadicus and the middle
lobe of the kidney. Its posterior boundary is the linea arcuata. The linea arcuata is a line
drawn from the acetabulum of the one side to the acetabulum of the other side.
The fovea pudendalis contains the posterior lobe of the kidney. The posterior boundary
is the anterior border of the first coccygeal vertebra. It gives passage to the nerve plexus
pudendo-hemorrhoidalis.
The ilium, the ischium, and the pubis join to form the cotyloid cavity, or acetabulum, in
which articulates the head of the femur. The floor of the cavity is perforated by a relatively
large round foramen.
The Ilium. Location.—The ilium, together with the lumbo-sacral vertebræ, forms the
roof of the pelvic cavity. It articulates at its inner border with the lumbo-sacral vertebræ,
postero-laterally with the ischium and at the cotyloid cavity with the pubis.
Description.—The ilium is remarkable for its development in the long axis of the
vertebral column. It is long and narrow; and mesially, where it is thickest it forms the
upper wall of the acetabulum. Anterior to the acetabulum it is outwardly concave, and
posterior to the acetabulum it is convex. The ilium fuses with the last dorsal vertebra and
with the lumbo-sacral vertebræ and is excavated on its internal face. This surface is
irregular and lodges the kidneys. This inner margin of the renal part enters with the square
extensions of the posterior excavation passing into the posterior iliac spine. The external
margin is the extension of the crista transversa and forms the processus ischiadicus.
Posteriorward the renal part of the ilium joins the ischium.
The ilia converge at the summits of the anterior sacral spines forming the ilio-lumbar
spines.
The ilium is joined to the square extensions of the last sacral vertebra by the symphysis
ilio-sacralis, to the larger part of the lumbar vertebræ by the sutura ilio-lumbalis, and to
the transverse processes of the last sacral vertebræ by the symphysis ilio-sacri.
The Ischium. Location.—The ischium is located in the postero-inferior part of the
pelvis. It joins superiorly with the ilium, and inferiorly with the pubis.
Description.—The ischium is smaller than the ilium and is a flattened, triangular-
shaped bone, thickest where it forms the posterior part of the acetabulum, becoming
thinner and broader as it extends backward. Posteriorly it forms the caudal extension. The
inferior border is turned slightly outward and is fused with the pubis. Between these bones
there is located the large oval ischiadic foramen, through which passes the ischiadic nerve.
This bone aids the ilium in the formation of the obturator foramen through which passes
the tendon of the internal obturator muscle. The lower part of the ischium which separates

the ischiadic foramen from the obturator foramen is called the ramus ascendens ossis
ischii.
The Pubis. Location.—The pubis is located along the inferior margin of the ischium
and extends further back than the posterior border of the ischium.
Description.—The pubis is a long, slender, rib-like bone. It forms the lower and front
portion of the acetabulum. The ischiadic foramen formed by the ischium and pubis is
single and nearly circular in fowls, double in pigeons, and in geese and ducks it is
elongate.

THE HIND LIMB (Fig. 4, Nos. 35, 47, 48, 49, 50, 51, 52, and 53; Fig. 12)

The pelvic, or hind, limb supports the body. The bones of each leg are the femur, which
constitutes the thigh, the tibia and the fibula, which represents the leg, and the metatarsus
and the phalanges, which form the foot.
The Femur (Fig. 12, A and B). Location.—The femur, or os femoris, the first bone of
the hind extremity, extends obliquely downward and forward, articulating with the
acetabulum above and the tibia, the fibula, and the patella below.
Description.—The femur, one of the largest, thickest, and strongest bones of the body,
belongs to the class of cylindrical bones, and presents for examination a shaft and two
extremities.
The superior, or proximal extremity, is provided with a head, caput femoris; the neck,
collum femoris; and the trochanter. The head is relatively small, and is marked by a
depression above for the round ligament which fills the cavity in the acetabular wall. Its
axis is nearly at right angles with the shaft. A neck joins it to the body at the proximal end.
External to the head of the femur is the trochanter. The trochanter presents an outer
convexity over which the tendon of the gluteus maximus extends to become inserted
below. The trochanteric ridge, which is opposite the articular head, presents an outer
flattened surface which possesses impressions for muscular attachments. The trochanteric
fossa, or fossa trochanterica, is shallow.
The shaft, or corpus femoris, is shorter than the tibia, is in general cylindrical, bent
forward, and the lower half is flattened and expanded transversely. A nutrient foramen is
located in the median portion of the shaft. The shaft shows muscular linear ridges.
The distal extremity is large in both directions and comprises the trochlea in front and
two condyles behind, one internal and one external. The condyles are separated by the
intercondyloid fossa, or fossa intercondyloidea, which is marked with pits for the
attachment of ligaments; and above this is the epitrochlear fossa.

Fig. 12.—Bones of the hind extremity.

A. Posterior view of femur.

B. Anterior view. 1, Shaft. 2, Proximal
extremity. 3, Distal extremity. 4, Articular head.
5, Trochanter major. 6, Shallow trochanteric
fossa. 7, Convexity over which the tendon of
the gluteus maximus glides. 8, External
condyle. 9, Internal condyle. 10, Nutrient
foramen. 11, Intercondyloid fossa. 12, Muscular
linear ridges. 13, Epitrochlear fossa.

C. Internal view of tibia.

D. External view. 1, Shaft. 2, Articular head. 3,
Distal end. 4, The rotular process. 5, The fibular
ridge. 6, External condyle. 7, Internal condyle.
8, Intercondyloid space. 9, Nutrient foramen.

E. Fibula, lateral view. 1, Articular head. 2, Its
attenuated portion.

F. Posterior view of metatarsus. 1, Trochlea for
inner or second digit. 2, Trochlea for middle or
third toe. 3, Trochlea for outer digit. 4, Bony
core for spur. 5, Bony canal for tendons. 6,
Groove for tendons. 7, Fossa intercondyloidea.

The inner condyle begins anteriorly as a ridge, and expands into a convexity which
attains its greatest breadth posteriorly where it becomes more flattened. The inner side of
the inner condyle is flattened and is provided with a tuberosity at its mid-part and a second
just above the posterior part of the condyle.
The outer condyle is formed in the same manner as the inner condyle. It is indented at
its broad, lower end by an angular groove, which, winding divides the posterior part of the
condyle into two convexities. The more external convex ridge and the groove dividing it
from the outer condyle are adapted to the head of the fibula. There is in this part a fibular
ridge and above this ridge a tuberosity.

The Tibia. Location.—The tibia (Fig. 12, D and C) extends obliquely downward and
backward from the knee-joint to the hock. It articulates above with the femur and, by its
procnemial process with the patella, below with the metatarsus, and laterally with the
fibula.
Description.—The tibia is the longest bone in the posterior limb, and possesses a shaft
and two extremities. It is largest at the proximal end and presents three faces.
The proximal extremity presents a semi-oval articular surface, not quite at right angles
with the shaft, which articulates with the condyles of the femur. The margin is raised
toward the anterior of the bone. The head of the tibia, or caput tibiæ, extends into a rotular
process which extends transversely, and is truncate. From the anterior of this process there
descends two vertical ridges; one near the angle of the rotular process, the procnemial
ridge; the other from the outer fibular angle, the ectocnemial ridge. On the outer side of
the intercondylar tuberosity there is a surface for the ligamentous union with the head of
the fibula; and a short distance below this there is a vertical ridge for the close attachment,
almost a fusion, with the fibula, called the fibular ridge.
The shaft, or corpus tibiæ is straight and the upper two-thirds subtrihedral; the lower
third oval. A nutrient foramen occurs near the upper postero-internal portion of the middle
third of the bone.
The distal extremity is much smaller than the proximal one; it is quadrangular in form.
The expanded inferior end of the tibia forms two articular condyles above which
posteriorly there is the epicondyloid fossa. The inner condyle, the larger, has a groove near
the lower end of the anterior part of the shaft, which deepens toward the intercondyloid
space. This intercondyloid fossa in young birds is covered by a strong ligament, which in
older birds, becomes ossified. On the lateral side of each condyle, there is a depression for
the attachment of ligaments.
The Patella. Location.—The patella, or knee-cap, thin and wide, articulates with the
procnemial process of the tibia, and with the deep trochlea of the distal end of the femur.
Description.—The patella is irregular in shape with three faces and three borders. The
posterior surface is articular. The other two surfaces are rough for tendinous attachment.
The patellar ligaments in old birds may become ossified.
In order to turn the foot in and out, the tibia not only turns around the inner condyle of
the femur, but also around the patella, so that the posterior surface turns outward and thus
turns outward the metatarsus and all the toes.
The Fibula. Location.—The fibula lies at the outer border of the tibia. It articulates
superiorly with the outer condyle of the femur, and laterally with the tibia.
Description.—The fibula is rudimentary; it is largest superiorly and tapers to a slender
point. The head is compressed laterally, and furnishes an upper and an inner articular
surface.
The Tarsus.—There exist, during fetal development of the chick, two rows of tarsal
bones which later become fused. The upper row fuses with the tibia and the lower with the
metatarsus. Therefore, in the adult, there is no tarsus.

The Metatarsus. Location.—The metatarsal bone extends downward and forward. In
birds it consists of one bone, which articulates superiorly with the inferior extremity of the
tibia. On the distal end it has a threefold trochlear arrangement which articulates with the
three principal digits.
Description.—The proximal extremity posteriorly has a process which may be
considered as a consolidation of originally separate metatarsal bones. The process at the
supero-posterior part of the metatarsus is called the hypotarsus of the tarso-metatarsus,
through which extends a canal called the hypotarsal canal, and which gives passage to
flexor tendons.
The proximal end of the metatarsus is ossified from one center of ossification forming
an epiphysis which caps the ends of the three original metatarsal bones that coalesce, first
with one another, then with the epiphysis, thus forming a single compound bone. Above
and just to the inside of the metatarsus there may occur a small bone which is imbedded in
ligaments and articulates with the inner proximal surface of the metatarsus. This has been
called by Gadow a sesamoid bone.
The shaft shows tendonal grooves which are best marked on the posterior surface. The
shaft is rounded at the sides and flattened on the anterior and posterior surfaces. At the
juncture of the middle and inferior thirds of the metatarsus there is a conical process
turned slightly backward, which serves as a base for the spur. The spur is a horny
structure.
At the distal extremity occurs the threefold trochlear arrangement mentioned above,
which incloses the fossa intercondyloidea. The inner trochlea is the broadest, and the outer
the narrowest. The inner trochlea articulates with the proximal end of the second, the
middle with the third, and the outer with the fourth toe.
The Phalanges. Location.—Most domestic fowls are provided with four digits, or toes;
the Houdan and Dorking are provided with five. In fowls with four toes the three principal
toes, the second, the third, and the fourth, are directed forward, and the first, or hallux, is
directed backward.
Description.—The last phalanx of each toe, called the ungual phalanx, is slightly
curved downward, is pointed anteriorly, like the claw of the cat or dog, and is covered
with a horny sheath. The articular ends of the joints of the phalanges are enlarged. The
base of the basal phalanx has two enlargements, the superior-inferior tubercles, or
tuberculum superius et inferius, between which is located the fossa articularis transversa.
Laterally the head has two condyles, condyli laterales, which are divided by the sulcus
longitudinalis. The bodies of the phalanges vary in form; they are superiorly rounded, but
inferiorly rounded, flat, or even somewhat concave. The distal extremity has an articular
trochlea.
The first toe, or digit, called the great toe, or hallux, is composed of three phalanges, or
segments. The first segment, or basal phalanx is considered a rudimentary metacarpal
bone; it is attached by a fibrous cartilaginous tissue to the inner posterior surface of the
inferior extremity of the metacarpal bone just below the spur.

The second toe, likewise composed of three phalanges, is directed forward. It articulates
with the inner trochlea located on the inferior metacarpal bone.
The third toe, made up of four phalanges, is the middle of the three forward toes. It
articulates with the middle trochlea of the inferior extremity of the metacarpal bone.
The fourth toe, is composed of five phalanges; it is, however, of approximately the
same length as the third, the segments being shorter. The fourth or outer toe articulates
with the outer trochlea of the distal extremity of the metacarpal bone.

ARTHROLOGY

Kinds of Joints.—Joints may be movable, immovable, or mixed. In
movable, or true joints the articular surface of each bone is covered by
cartilage. The bones are held together by ligaments, the capsular one often
surrounding the joint and enclosing the synovial membrane. In some joints
there is a pad of fibrous cartilage interposed between the two articular
cartilages. Such a pad, called a meniscus, adds to the elasticity and the free
movement of the joint. Movable joints form the most numerous class; they
are for the most part found in the limbs.
In an immovable joint there is only a thin layer of fibrous or cartilaginous
material interposed between the bones. The fibrous layer of the periosteum
of both bones unite to cover the connecting material and becomes attached
to the same, thus serving as a ligament. If the connecting material is fibrous,
the joint is called a suture; if cartilaginous, a synchondrosis. These joints are
found in the skull and in the pelvis.
The term mixed is used with reference, not to the motion in joints, but to
their structure, which partakes of the nature of both the movable and
immovable. The bones are firmly joined by a strong interposed pad of
fibrous cartilage to which also is adherent the ligaments of the joint. There
are no capsular ligaments; the cartilaginous pad or disc is softer toward its
center, where occasionally there may be one, or even two, narrow cavities.
Authorities differ as to whether such cavities are lined by synovial
membrane or not. Since there are really no frictional surfaces in such a
joint, motion depends upon the flexibility of the disc. The joints between
the vertebral centra afford the best illustration of the mixed class.
Movement of Joints.—The movements admissible in joints may be
divided into four kinds: gliding, angular movement, circumduction, and
rotation. These movements are often, however, more or less combined in

the various joints. It is seldom that there occurs only one kind of motion in
any particular joint.
Gliding movement is the most simple kind of motion that can take place
in a joint, one surface gliding or moving over another without any angular
or rotary movement.
Angular movement occurs only between the long bones. By it the angle
between the two bones is increased or diminished. It may take place in four
directions: forward and backward, consisting of flexion and extension; or
inward and outward from the medial line of the body, consisting of
adduction and abduction. Abduction of a limb is movement away from the
medial line of the body. Adduction of a limb is movement toward the
medial line of the body.
Circumduction is that limited degree of motion which takes place
between the head of a bone and its articular cavity, whilst the extremity and
sides of the limb are made to circumscribe a conical space, the base of
which corresponds with the inferior extremity of the limb, the apex with the
articular cavity; this kind of motion is best seen in the shoulder- and hip-
joint.
Rotation is the movement of a bone upon an axis, which is the axis of the
pivot on which the bone turns, as in the articulation between the atlas and
axis, when the odontoid process serves as a pivot around which the atlas
turns; or else is the axis of a pivotlike process which turns within a ring, as
in the rotation of the radius upon the humerus.
Pronation is a form of rotation in which the inferior extremity of the
radius passes before the ulna, and thus causes the hand to execute a kind of
rotation from without inward.
Supination is a form of rotation in which the movement of the forearm
and hand are carried outward so that the anterior surface of the latter
becomes superior.
The Ligamentous Structure.—Ligaments are dense, fibrous, connecting
structures. They are made up principally of white fibrous tissue and exist in
all true joints.
There are four kinds of ligaments associated with true joints:
The first kind, the capsular ligament which encloses all true joints, is thin
and consists of interlaced fibers attached to the bone at the edges of the

articular cartilages. It either partly or wholly surrounds the joint, enclosing
and protecting a synovial apparatus, which, by secreting a liquid resembling
serum, lubricates the joint to prevent friction.
The second kind, the binding or lateral ligaments, consist of flattened or
rounded cords or bands of fibrous tissue. Such a ligament extends from one
bone to the other, and firmly attached to their roughened surfaces, holds the
bones in place and at the same time allows the required amount of motion.
The third kind, located between the joints, is called interosseous
ligament.
The fourth kind, called the annular ligament binds down and protects the
tendons.
Ligaments of the Ear[2].—The concha of the ear is provided with a
superior and an inferior ligament.
2. The classification of Gadow is used.

Ligaments of the Jaw.—The articulations of the lower jaw are complex.
The freely movable articulation is between the inferior maxilla and the
quadrate. Less freely movable articulations are formed by the quadrate with
the temporal, the zygomatic and the pterygoid. A lateral ligament of the jaw,
the articulo-jugale extends from the posterior border of the inner wing of
the os articulare of the inferior maxilla (Fig. 8, No. 10, and Fig. 19, No. 15)
to the outer border of the os quadrato jugulare.
A lateral temporo-maxillary ligament extends from the outer surface of
the temporal bone to the outer border of the os articulare of the inferior
maxilla (Fig. 8, No. 11, and Fig. 19, No. 14).
Ligaments of the Vertebræ.—In each space between the bodies of the
vertebræ there is a meniscus intervertebralis. This meniscus is analogous to
the annulus fibrosus of mammals (Gadow), which, is possibly formed as a
protrusion of the anterior surface of the vertebral body. The meniscus or
disc may develop into a ring-shaped structure, the true meniscus, or it may
develop to different degrees as an extension of the vertebral body surface,
and become, as in the dorsal and lumbar regions, fused with the vertebral
segments, in which case it is called the annulus fibrosus.
The vertebral disc which is connected with the atlas and which is fused
with that bone, represents the first meniscus, which is called the ligamentum

transversum atlantis. This, as well as other ligaments of the spinal column,
may become ossified.
The ligament which is located between those vertebral bodies which face
each other and is inside the joint cavity, is called the ligamentum
suspensorium corporum vertebralium. It passes through the central opening
of the meniscus and lies exactly in the long axis of the body of the vertebra.
The first ligament of the neck is the ligamentum suspensorium dentis
epistrophei. The ligamentum capsulare atlantico-occipitale and the
ligamentum capsulare atlantico-epistrophicum odontoideum are two parts
of the joint capsule of the vertebral body. Other ligaments of this part are
the membranæ obturatoriæ intervertebrales posteriores, which are located
between the semicircular rims of the neck vertebræ.
The ligamentum transversum atlantis surrounds the occipital condyle.
The ligamentum nuchæ is a thin, membranous, ribbon-like structure
which lies between the muscles of the right and those of the left side of the
middle, and the lower part on the posterior of the neck, and ends in
attachments to the superior spines of the cervical vertebræ.
The ligamentum elasticum interspinale profundum and the ligamentum
elasticum interspinale superficiale and the three last named are the
ligaments which keep the neck of the fowl in the s-shape, without the action
of the muscles.
The ligamentum capsulare obliquum connects the facets of the oblique
processes.
Ligaments of the Ribs.—The thick inferior end of the sternal portion of
the true rib has two small articular heads, which articulate with two
depressions in the articular surface of the sternum. This articulation is held
firm by a capsular ligament.
The upper end of the sternal rib forms an almost perfect right angle with
the inferior end of the dorsal rib with which it is connected by a joint
provided with a synovial apparatus and a capsular ligament. This
arrangement allows free movement outward and inward and is the main
joint in respiration.
The upper end of the dorsal portion of the rib articulates with the dorsal
vertebra. The joint formed by the articular head with the body of the
vertebra is provided with a capsular ligament. The tubercle of the rib

articulates with the facet on the transverse process of the dorsal vertebra,
and is provided with a transverse ligament, called the ligamentum
transversum externum. It is also provided with a capsular ligament.
The ligamentum triangulare connects each processus uncinatus with the
succeeding rib. This ligament is in the form of a membranous sheet, or
aponeurosis.
Ligaments of the Sternum (Fig. 13).—The external and the internal
notches of the sternum are bridged over with a thin membrane which gives
an extensive surface for muscular attachments. The sternal muscles overlie
this portion.

Fig. 13.—Muscles of the fore extremity.
Inside view. 1, Lateral external process
of sternum. 2, Lateral internal process of
same. 3, Ligament of the external notch.
4, Ligament of the internal notch. 5,
Pectoralis major. 5a, Its fan-shaped
expansion at shoulder-joint laid back. 6,
Pectoralis tertius. 7, The coracoid. 8,
Biceps. 8a, Its long head. 8b, Its short
head. 9, Pectoralis secundus. 10, Rectus
abdominis. 11, Teres et infraspinatus.
12, Deltoid. 13, Capsular ligament. 14,
Teres minor. 15, Coraco-brachialis. 16,
Serratus magnus anticus. 17, Extensor
metacarpi radialis longior. 18, Pronator
brevis. 19, Flexor carpi ulnaris. 20,
Flexor carpi ulnaris brevior. 21, Flexor
digitorum profundus. 22, Extensor
indicis longus. 23, Extensor ossis
metacarpi pollicis. 24, Humerus. 25,
Shoulder. 26, Elbow. 27, Carpus. 28,
Section through vertebra. 29, Keel of
sternum. 28a, Flexor brevis pollicis.
29a, Extensor proprius pollicis. 30,
Flexor minimi digiti brevis. 31,
Interosseous palmaris. 32, Interosseous
palmaris.

The sternum is connected by a fibrous mass with the inferior portion of
the clavicle, or hypocledium (Fig. 57), the claviculosternal ligament.

The inferior narrow elongated end of the coracoid forms with the sternum
a true articulation, which is provided with a capsular ligament, the
ligamentum capsulare. Capsular ligaments occur at the articulations
between the sternum and ribs.
Ligaments of the Shoulder-joint (Fig. 13).—The shoulder-joint is made
up of the scapula, the humerus, and the coracoid. The ends of these three
bones form the foramen triosseum (Fig. 15, No. A, 7) through which passes
the tendon of the elevator muscle of the wing.
The furcula, independent of the shoulder-joint or girdle, is attached to the
supero-internal part of the proximal end of the coracoid by fibrous
connective tissue; it is also connected to the other bones of the shoulder-
joint by the ligamentum coraco-furculare and the ligamentum furculo-
scapulare.
The ligamentum coraco-scapulare extends from the tuberosity of the
furcula to the coracoid and to the processus furcularis of the scapula.
The ligamentum coracoido-scapulare externum extends between the
external tuberosity of the coracoid, the tuberosity of the scapula, and the
humerus.
The ligamentum coracoideo-scapulare inferius extends from the coracoid
to the inner tubercle of the scapula.
Another long, broad ligament belongs to the episternal apparatus.
The shoulder-joint is provided with a wide, loose, capsular ligament
(Fig. 13, No. 13). Attached to the humerus are four other ligaments, of
which three pass from the anterior end of the coracoid and the fourth from
the scapula. The latter are as follows: first, the supero-anterior ligamentum
humero-coracoideum, which extends from the small tubercle of the
humerus to the coracoid bone; second, the antero-inferior ligamentum
humero-coracoideum, which extends from the humerus to the coracoid;
third, the ligamentum coraco-humerale, which extends from the coracoid to
the large tubercle of the humerus; fourth, the ligamentum humero-scapulare
which extends between the processus humeralis of the scapula and the head
of the humerus.
Ligaments of the Elbow-joint (Fig. 14).—The elbow-joint is made up
of the ulna, radius and the humerus. The ligaments of the elbow-joint are as
follows: the ligamentum capsulare cubiti, or capsular ligament, which

extends from the processus cubitalis of the humerus to the processus
olecranalis coracoideus of the ulna and to the tuberositas radii of the radius
(Fig. 15, No 5).
The ligamentum laterale cubiti externum connects the outer humeral
distal extremity with the head of the radius (Fig. 15, No. 2).
The ligamentum laterale cubiti internum lies between the inner distal
extremity of the humerus and the tuberculum internum of the ulna (Fig. 14,
No. 9).
The ligamentum annulare radii originates on the olecranon, surrounds
the head of the radius, and is attached to the tuberculum internum of the
ulna (Fig. 15, No. 3).
The ligamentum cubiti teres extends from the head of the radius to the
upper end of the ulna (Fig. 15, No. 4).

Fig. 14.—Muscles and ligaments of the
arm and forearm of a hen.

A. External view. 1, Expansor
secundarium. 2, Tensor patagii longus.
3, Tensor patagii brevis. 5, Brachialis
anticus. 6, Pronator longus. 7, Supinator
brevis. 8, Extensor indicis brevis. 10,
Scapulo-humeralis.

B. Internal view. 9, Ligamentum laterale
cubiti internum.

The ligamentum transversum spreads out between the head of the ulna
and the radius, thus uniting the two bones, and limiting supination (Fig. 15,

No. 1).
Ligaments of the Carpal Joint.—The carpal joint is made up of the
ulna, radius, the two carpal bones and the metacarpus.
There are two strong ligamenta obliqua carpi ulnaris which extend from
the processus styloideus of the ulna to the tuberculum posterius carpi
ulnaris of the os carpi ulnaris.
The ligamentum posticum ulnare carpi ulnaris extends from the
processus styloideus of the ulna to the os carpi ulnaris.

Fig. 15.—Ligaments of the arm and
forearm of a hen.

A. The scapulo-coraco-humeral
articulation. 1, Proximal end of the
humerus. 2, Articular head of humerus.
3, The coracoid. 4, Proximal end of the
clavicle. 5, Tendon of pectoralis tertius.
6, Tendon of pectoralis secundus. 7,
Opening or foramen triossium through
which the tendon of the elevator of the
wing passes. (Pectoralis secundus.) 8,
Broken end of scapula.

B. 1, Ligamentum transversum. 2,
Ligamentum laterale cubiti externum. 3,
Ligamentum annulare radii. 4,
Ligamentum cubiti teres. 5, A portion of
the ligamentum capsulare cubiti. 6,
Distal extremity of humerus. 7, Ulna. 8,
Radius.

C. Muscles of the outside surface of the
arm. 1, Tensor patagii longus. 2,
Extensor digitorum communis. 3,
Tensor patagii brevis. 4, Anconeus. 5,
Flexor carpi ulnaris. 6, Biceps. 7,
Triceps. 8. Deltoid. 9, Brachialis
anticus. 10, Flexor metacarpi radialis.
11, Extensor ossis metacarpi pollicis.
12, Extensor metacarpi radialis longior.
13, Extensor indicis longus.

The ligamentum ulnare carpi radialis is a short ribbon-like ligament
which passes over the above-mentioned ligaments and is attached to the
inner surface of the os carpus radialis.

The ligamentum ulnare carpi radialis internum is a strong ligament
which originates on the inner part of the elbow. It extends to the upper rim
of the base of the main digit.
The ligamentum radiale carpi radialis externum originates on the outside
of the head of the middle digit and inserts to the superior tuberculum carpi
radialis of the radius.
The ligamentum carpi radialis internum, a short ligament, extends from
the inside of the head of the main digit to the inner rim of the carpi radialis.
The ligamentum carpi interosseum is located between the carpal bones.
The ligamentum ulnare metacarpi internum is spread out between the
processus styloideus of the ulna and the tuberositas muscularis on the upper
side of the middle finger base at a point where the second and the third
metacarpi separate.
The ligamentum ulnare metacarpi externum extends from the tubercle of
the distal extremity of the ulna, on the dorsal side, to the tubercle on the
base of the metacarpus.
Ligamentum radiale metacarpi extends from the head of the inner digit to
a point near the tuberculum muscularis of the radius.
The ligamentum transversum ossis carpi radialis et metacarpi is located
between the inferior tuberculum ossis carpi radialis and the first metacarpal
bone.
There is another ligament between the tuberculum superiorus carpi
radialis and the first metacarpal bone.
The ligamentum ossis carpi radialis internum et metacarpi extends from
the inner surface of the carpus radialis to the tuberositas muscularis of the
radius.
The ligamentum ossis carpi ulnaris externum et metacarpi extends from
the ulnar carpal bone to the tuberculum of the metacarpal bone.
The ligamentum ossis carpi ulnaris internum et metacarpi extends from
the processus uncinatus of the ulnar carpal bone to the tuberositas
muscularis of the metacarpal bone.
Ligaments of the Finger.—The ligamentum pollicare connects the
thumb with the first metacarpal bone.

The ligamentum anterius ossis metacarpi et primæ phalangis digiti
secundi extends from the tuberculum articulare metacarpi, of the proximal
end of the metacarpus, to the tuberculum articulare of the first phalanx of
the second or large finger. Similarly attached, are also an internal and a
posterior ligament, or ligamentum internum and ligamentum posterius.
The three phalanges are all provided with capsular ligaments, or
ligamenta capsularia, which bind together the several phalanges.
The small or third finger is connected to the metacarpus by a capsular
ligament, the ligamentum capsulare, and by an interosseous ligament, or
ligamentum interosseum digitorum, to the first phalanx of the second finger.
Ligaments of the Pelvis.—The obturator foramen, formed by the ilium
and the ischium, is covered by a broad membranous ligament (Fig. 4, No.
29).
The oblong foramen, or foramen oblongum, and the foramen
ischiadicum, formed by the ischium and the pubis are covered by broad
membranous ligaments (Fig. 4, Nos. 29 and 60).
Poupart’s ligament or ligamentum Poupartii, quite small in fowls,
extends from the anterior lower rim of the ilium to the pelvic cavity, and is
inserted at the bottom of the acetabulum.
Another broad ligament originates from the posterior rim of the ischium
and is attached to the square surface of the first coccygeal vertebra.
The ilio-pubic ligament extends from the pubic spine to the last
rudimentary rib.
Ligaments of the Hip-joint (Fig. 25, F).—The hip-joint is made up of
the ilium, ischium, pubis and femur and is a deep ball-and-socket joint. The
cavity or acetabulum is called a cotyloid cavity.
The hip-joint is provided with three ligaments.
The ligamentum capsulare femoris is attached around the rim of the
cotyloid cavity and around the rim of the articular head of the femur (Fig.
25, No. F, 4).
The ligamentum teres, or round ligament, is a very short ligament which
closes the hole at the floor of the cotyloid cavity, at which point it is
attached. It is also attached to the head of the femur.

The ligamentum ilio-sacrale strengthens the hip-joint capsule. It passes
from the lower anterior rim of the os ilii, extending over the capsule to the
neck of the femur to which it is attached.
The Ligaments of the Knee-joint (Figs. 16 and 17).—The knee-joint is
made up of the femur, patella, tibia and fibula, and is provided with the
following ligaments:
The ligamentum extero-laterale genu is a strong ligament extending from
the condylus externus femoris, or external femoral condyle to the outer
surface of the head of the fibula, or capitulum fibulæ. From this head there
passes inward, a strong ligament to a point between the femur and fibula
(Fig. 25, No. D, 4).

Fig. 16.—Ligaments and muscles of the hind extremity.

A. A transverse section through the tibial or tarsal cartilage, front view. 1,
Gastrocnemius tendon. 2, Flexor perforatus annularis primus pedis. 3, Flexor
perforans digitorum profundus. 4, Flexor perforatus indicis secundi pedis. 5,
Extensor longus hallucis. 6, The articular surface. 7, Ligamentum capsulare ossis
tarsi. 8, Flexor perforatus medius secundus pedis. 9, Flexor perforatus indicis
secundus pedis. 10, Tendons of the extensor muscles.

B. Knee-joint. Inside view of femoro-tibial articulation. 1, Anterior ligamentum
cruciatum. 2, Internal ligamentum laterale genu. 3, Anterior patellar ligament. 4,
Patella. 5, Distal end of femur. 6, Proximal end of tibia. 7, Location of meniscus
or pad of fibrocartilage.

C. Anterior view of tibio-tarsal articulation. 1, Distal end of tibia. 2, Its articular
surface. 3, Ligamentum anticum. 4, Proximal end of metacarpus. 6, Pad of
fibrocartilage.

D. The dorsal surface of the coccyx. 1, The bilobate oil gland. 2, Its duct. 3,
Levator coccygis.

E. Inside view of pelvis and thigh. 1, Obturator internus. 2, Ambiens. 3, Vastus
internus. 4, Internal ligamentum laterale genu. 5, Tibialis anticus. 6, Loop
through which the tibialis anticus passes. 7, Adductors of the thigh. 8, Loop for
the extensor tendon.

The ligamentum intero-laterale genu extends from the outer surface of
the internal condyle of the tibia, or condylus internus tibiæ. It gives off a
thin ligamentous slip which enters the joint and is attached to the inner half-

moon shaped pad of fibrous cartilage, or meniscus, which it draws
backward by the flexion of the knee (Fig. 16, No. B, 2).
The ligamentum popliteum arises from the fossa poplitea of the distal
extremity of the femur and extends downward to the posterior rim of the
head of the tibia.
The anterior ligamentum cruciatum genu originates from the fossa
poplitea and extends outward antero-laterally to the rim of the head of the
tibia (Fig. 25, No. 6).
The posterior ligamentum cruciatum genu is a short, strong ligament
which originates from the cavity of the internal condyle of the femur, or
condylus internus femoris, and inserts into the internal glenoid cavity of the
tibia (Fig. 25, No. 1) or cavitas glenoidalis interna.
The meniscus of the femoro-tibial articulation is divided into four parts,
as follows: first, the internal adhesio cornu antici cartilaginis lunatæ;
second, the posterior adhesio cornu antici cartilaginis lunatæ; third, the
external cornu cartilaginis lunatæ; fourth, the anterior cornu antici
cartilaginis lunatæ. The latter originates between the condyles and passes
around the ligamentum cruciatum genu posticum (Fig. 16, No. B, 7).
The inner semi-lunar fibrous cartilage is well developed and is joined by
two ligaments between the femoral and the tibial surfaces (Fig. 25, No. 1).
The external semi-lunar cartilage lies in a cavity between the external
femoral condyle and the head of the fibula (Fig. 25, No. 2).
The fibrous cartilages are bound posteriorly by a ligament, and by a
second ligament to the head of the fibula, or capitulum fibulæ. Both pads of
fibrous cartilage are connected by a transverse ligament called the
ligamentum transversale commune (Fig. 25, No. 5).
The patella is provided with several ligaments, as follows:
The anterior patellar ligament, broad, strong, and irregular in thickness,
extends from the inferior margin of the patella to the rim of the second tibial
crest (Fig. 16, No. B, 3).
The ligamentum capsulare capituli fibulæ is spread out between the head
of the fibula, or capitulum fibulæ, and the superficies glenoidalis peronea
tibiæ.

Fig. 17.—Muscles and tendons of the
head and posterior extremity.

A. Section of neck with superficial
muscles removed. 1, Obliquo-
transversales. 2, Interspinales. 3,
Intertransversales. 4, Interarticulares.

B. Head showing muscles. 1, Beak. 2,
Nostril. 3, Tongue. 4, Sublingual
salivary gland. 5, Pterygoideus. 6,
Stylo-hyoideus. 7, Temporal. 8, Flexor
capitis inferior. 9, Rectus capitis
lateralis. 10, Rectus capitis posticus
major. 11, Trachelo-mastoideus. 12,
Eye. 13, Mylo-hyoideus. 14, Genio-
hyoideus. 15, Biventer maxilla. 16,
Digastricus. 17, Rectus capitis anterior
minor.

C. Foot of hen showing tendons. 1,
Flexor perforans digitorum profundus.
2, Flexor perforatus medius primus
pedis. 3, Sheath at joint through which
tendon passes. 4, Flexor perforatus
indicis primus pedis. 5, Flexor
perforatus medius secundus pedis. 6,
Flexor perforatus annularis primus
pedis. 7, Flexor longus hallucis.

D. Outside view of leg of hen. 1, Biceps
flexor cruris. 2, Semitendinosus. 3,
Loop through which biceps flexor cruris
passes. 4, Tibialis anticus. 5, Flexor
perforatus indicis secundus pedis. 6,
Flexor perforatus medius primus pedis.

7, Gastrocnemius. 8, Flexor perforatus
annularis primus pedis. 9, Flexor
perforatus medius secundus pedis. 10,
Extensor longus hallucis.

The ligamentum tibio-fibulare extends from the head of the fibula, or
capitulum fibulæ, to the inner surface of the external crest, or crista externa
tibiæ, of the tibia (Fig. 25, No. 3).
The ligamentum interosseum is a delicate ligament located between the
tibia and fibula (Fig. 25, No. 4) which very early becomes ossified.
Ligaments of the Tibio-metatarsal Joint (Fig. 16).—The tibio-tarsal
joint is made up of the tibia and metatarsus.
The ligamentum capsulare ossis tibio-metatarsi connects the tibia and the
metatarsus and surrounds the joint (Fig. 16, Nos. A, 7 and C, 7).
The ligamentum externum, a long strong ligament, originates on the
upper and outer surface of the external condyle, or condylus externus of the
tibia and is attached to the upper rim of the os metatarsi (Fig. 23, No. 15).
The ligamentum anticum is spread out between the fossa
intercondyloidea of the tibia and the tuberculum ossis metatarsi of the
proximal end of the metatarsus (Fig. 16, No. C, 3). Just posterior to this
ligament, there is an interosseous ligament, the ligamentum interosseum.
A semi-lunar pad of fibrous cartilage, the cartilago semi-lunaris is
located between the outer distal extremity of the tibia and upper articular
surface of the metatarsus (Fig. 16, No. C, 6). Its concave portion is directed
anteriorly and receives an insertion from the ligamentum externum, or
external ligament.
The tendon Achillis (Fig. 16, No. A, 1) may become ossified.
Ligaments of the Toes (Fig. 16).—In addition to the capsular ligaments,
which all true joints have, we find the following in connection with the
toes:
The ligamentum superius and the ligamentum inferius connect the second
toe with the great toe, or hallux.
The ligamentum laterale externum and the ligamentum laterale internum
unite the bases of the second, third and fourth toes to the lateral faces of the
trochleas of the inferior extremity of the metatarsus.

The bases of the toes are held together by the ligamenta transversa. All
the rest of the toes are held together by the ligamenta capsularia digitorum
pedis and by two lateral ligaments, namely: the ligamentum laterale
externum and the ligamentum laterale internum.

MYOLOGY

Kinds and Structure of Muscles.—Muscles are highly specialized
structures which have the property of contractility when stimulated, and
thus produce motion. Muscular tissue is sometimes called flesh. Two kinds
of muscles are recognized; muscles of locomotion and visceral muscles.
The muscles of locomotion may be in masses of different shape attached
to the skin, the dermal, or to the skin and skeletal structure, the dermo-
osseous, or from one bone to another, the skeletal. The visceral muscles
form sheets and make up a portion of the wall of many of the hollow
organs, such as the intestines, the stomach, the gizzard, the esophagus, and
the blood-vessels. A special type of muscle forms the heart.
When classified with reference to structure, muscular tissue is divided
into three types, as follows: voluntary-striated, involuntary, and
involuntary-striated. The microscopic examination of each of these types of
muscle shows it to be made up of fibers, these fibers to be made up of
muscle cells, the muscle cell to be inclosed in a delicate tubular sheath, or
membrane, called the sarcolemma. This membrane, tough and elastic,
isolates each fiber. The bundles of fibers, called fasciculi, are surrounded by
a fibrous sheath, which is called the perimysium internum; and the entire
muscle has likewise an investing sheath of connective tissue, called the
perimysium externum. The muscular cells show a longitudinal striation
marking the fibrillæ, and they also show a cross striation. Nuclei are found
just beneath the covering, or sarcolemma, in the striated muscle cell (Fig.
77, No. 2). In the involuntary and in the involuntary-striated muscle cell,
the nuclei are centrally located.
The voluntary-striated muscles consist of cylindrical fibers and with a
few exceptions, are under the control of the will. A muscle of this type, the
regular skeletal form, usually has at each extremity a fibrous structure,

called a tendon, by means of which it is attached to the bones. The
intermediate fleshy portion of the muscle, in case of considerable bulk, is
called the belly of the muscle.
The involuntary, non-striated, or smooth muscle, cells are spindle-
shaped, long, and pale in color (Fig. 77, No. 1). The cells lie end to end
forming fibers. These fibers do not terminate in tendons, but are arranged in
sheets and aid in forming the walls of the digestive tract, to which they give
the power of contraction and expansion.
Involuntary-striated, or heart muscle (Fig. 77, No. 4), occupies an
intermediate position between the two muscles just described. It is
composed of cells which branch, are somewhat rectangular. They possess
both longitudinal and transverse striation. Among the fibers is found a small
amount of connective tissue, as in the former types of muscle, which gives
support to the blood-vessels and nerves.
Fascia.—The term fascia is applied to membranous expansions, differing
materially in strength, texture, and relations. Fascia is composed of loosely
arranged white fibrous connective tissue. At least two layers may usually be
distinguished, the superficial fascia and the deep fascia.
Below the skin is the superficial fascia, which forms a continuous
covering over the whole body and serves to attach the skin to the underlying
structure.
The deep fascia more densely constructed, may be attached to the
skeleton, ligaments, and tendons.
When the fascia spreads out, becomes denser, and acts as a continuation
of a muscle, it is called an aponeurosis.
The Muscular Nomenclature.—In the fowl there are 162 muscles,
single or in pairs. These muscles are named from their location, as the
lingualis; others from their attachments, as the dermo-temporalis; some
from their form, as the rhomboideus; others from their use, as the flexor or
extensor; and still others from their direction, as the transversus.

The Dermal Muscles

Birds are provided with a system of delicate muscles divided into
numerous fasciculi, which harmoniously act upon the feather quills and
collectively agitate the plumage. These are the dermal muscles. This group
is divided into two subgroups: the true dermal muscles, that is, those that
have their origin and insertion to the under surface of the skin; and the
dermo-osseous, those that originate on the surface of some bone and insert
to the inner surface of the skin.

TRUE DERMAL MUSCLES

Dermo-frontalis
Dermo-dorsalis
Dermo-tensor patagii
Dermo-humeralis
Dermo-pectoralis

Dermo-frontalis.[3] Location.—This muscle is somewhat rudimentary
and may be entirely absent. It is located in the frontal region and is about 2
or 3 centimeters long and not so wide.
3. The classification of Shufeldt is used.

Origin and Insertion.—Closely attached to the skin.
Shape.—Flat and rather rectangular.
Relations.—Superiorly with the skin and inferiorly with the frontal
bones.
Action.—By contraction the feathers on the top of the head lie flat. Those
above the eyes are elevated.
Dermo-dorsalis. Location.—In the median line of the neck and back.
Origin and Insertion.—Adhering closely to the skin, it generally
becomes lost at the occiput; it is most highly developed in the mid-cervical
region, and it gradually disappears over the caudal region.

Shape.—Delicate and ribbon-shaped.
Relations.—Superiorly it is attached to the skin. Fat sometimes surrounds
the muscle.
Action.—By contraction it raises the feathers along the superior part of
the neck and dorsal region.
Dermo-tensor Patagii. Location.—Between the root of the neck and top
of the shoulder.
Origin and Insertion.—Attached to the skin in the region of the anterior
part of the root of the neck, some fibers passing obliquely upward and blend
with fibers of the dermo-temporalis. It blends, by a slender tendon, with that
of the tensor patagii longus.
Shape.—A bundle of muscular fibers later becomes thin, delicate, and
triangular in shape.
Relations.—Externally to the skin.
Action.—Auxiliary to the tensor patagii longus. A tensor of this region.
The patagii are associated with the wing fold of skin which fills the angle
between the arm and forearm. This fold contains elastic tissue and muscle.
Dermo-humeralis. Location.—Lateral thoracic region.
Origin and Insertion.—Fan-like delicate fibers from the skin in the
abdominal integument, contracting into a long narrow fasciculus of fibers,
again spreading out in fan-shape to be inserted to the tendon of the
pectoralis major, just below its insertion.
Shape.—Triangular, fan-shape.
Relations.—Superiorly with the skin.
Action.—Controls the skin in this region. The anterior end being fixed,
the muscles are raised; and the posterior end acting as the fixed point, the
feathers are caused to lie close to the body.
Dermo-pectoralis. Location.—On each side of the chest, lying in a
longitudinal manner.
Origin and Insertion.—Attached to the skin on either side of the thorax
corresponding to the dermo-dorsalis. Anteriorly it disappears over the
region of the origin of the cleido-trachealis, and posteriorly just behind the
tips of the post-pubic parts of the pelvis.
Shape.—Thin, delicate.

Relations.—Superiorly with the skin.
Action.—The anterior part acting as the fixed point, the feathers of the
chest are raised; and the posterior end acting as the fixed point, the feathers
are made to lie flat.

THE DERMO-OSSEOUS MUSCLES

Dermo-temporalis
Platysma myoides
Dermo-cleido dorsalis
Cleido-trachealis
Dermo-spinalis
Dermo-iliacus
Dermo-ulnaris

Dermo-temporalis (Fig. 18, No. 1). Location.—From the temporal
region down the side of the neck to the anterior part of the thoracic region.
Origin.—By a broad tendinous attachment from a small depression
above and anterior to the temporal fossa. From here the fibers pass upward
and backward and then downward.
Insertion.—A few fibers blend with those of the cleido-trachealis. The
fibers are then lost upon the skin in front and opposite the shoulder-joint.
Some of the fibers blend with those of the dermo-tensor patagii.
Shape.—Long, flat, and ribbon-shaped. The lower portion consists of
delicate fibers.
Relations.—Superior to the temporal muscle and sphenotic process.
Superior to the cleido-trachealis and inferiorly to the shoulder-joint. The
superior portion touches the skin throughout its entire length.
Action.—A tensor of the lateral cervical integument. It is an auxiliary to
the tensor patagii.
Platysma Myoides. Location.—The inferior portion of the throat.
Origin.—From the lower margin of the rami of the jaw. Just inferior to
the attachment of the masseter.

Fig. 18.—Muscles of the upper neck
region, 1, Dermo-temporalis. 2, Cornu
of the os hyoideum. 3, Carotid artery. 4,
Jugular vein. 5, Pneumogastric nerve. 6,
Esophagus. 7, Trachea.

Insertion.—From the point of origin it spreads out into a thin fan-like
layer and meets its fellow in the median raphe. It is attached to the skin in
this region.
Shape.—A very thin fan-shaped muscle.
Relations.—Closely adherent to the skin.
Action.—Assists in supporting the lingual apparatus and superior larynx.
Compresses and elevates the part.
Dermo-cleido Dorsalis. Location.—Anterior shoulder region.
Origin.—From the upper mesial part of the clavicular bone.
Insertion.—Three fasciculi forming a fan-like arrangement attached to
the skin in the shoulder-joint and scapular region. The extremities of the
fasciculi may meet in the median line of the dorsal region and merge with
the dermo-dorsalis.
Shape.—Three fasciculi forming a fan-shaped radiation.

Relations.—Superiorly with the skin. Inferiorly with the shoulder-joint.
Action.—Contracting with the origin as the fixed point, they brace the
skin over the forepart of the back. With the integumental attachment as the
fixed point, they aid in the act of respiration.
Cleido-trachealis. Location.—Extending from the shoulder to the
superior laryngeal region.
Origin.—From a small area on the antero-inner part of the middle of the
arm of the furcula.
Insertion.—The fibers pass upward and become flattened and attached to
the skin and dermo-temporalis muscle. They touch each other on the
anterior border of the superior larynx, the trachea, and the skin over these
parts.
Shape.—A slender bundle of muscles.
Relations.—Superiorly the skin, and internally the larynx and the trachea.
Action.—Controls the skin region of this part of the neck.
Dermo-spinalis. Location.—In the region of the shoulder.
Origin.—In an attenuated fascia from the crest of the neural spines of the
first, the second, and the third dorsal vertebræ.
Insertion.—To the skin in a broad pale stratum, over the scapular region.
Shape.—Thin, pale, and very delicate.
Relations.—Superiorly with the skin, and inferiorly with the shoulder.
Action.—Controls the skin of the region.
Dermo-iliacus. Location.—Along the back on either side of the spine.
Origin.—From the inner angle of the marginal portion of the antero-
dorsal border of the ilium.
Insertion.—Passing forward as a delicate band it spreads out and
becomes lost in the skin of the shoulder region.
Shape.—Thin, delicate, and ribbon-shaped.
Relations.—Superiorly with the skin.
Action.—If the posterior end is fixed, it will cause the feathers to lie close
to the skin. Its action would then be opposite to the dermo-dorsalis.
Dermo-ulnaris. Location.—Outer surface of the anterior upper costal
and the posterior humeral region.

Origin.—By a thin fascia from the outer part of the third and the fourth
true ribs at the base of their epineural appendages. Also from the fascia
between them.
Insertion.—The fibers pass forward and upward as a thick muscular
bundle and is loosely attached to the skin at a point just back of the
humerus. The tendon later becomes spread out and attached to the fascia as
far as the elbow-joint. It covers the olecranon of the ulna.
Shape.—At first rather thick, fascicular-like; later becomes tendinous;
and at its attachment it becomes spread out over the olecranon.
Relation.—Inferiorly with the ribs and humerus, and externally with the
skin.
Action.—A depressor of the humeral region.

The Skeletal Muscles

THE MUSCLES OF THE HEAD

Temporal
Masseter
Biventer maxillæ
Entotympanicus
Pterygoideus internus
Pterygoideus externus
Digastricus

Temporal (Fig. 19, No. 4). Location.—Occupies the temporal fossa.
Origin.—From the mesian line of the sphenotic process, and the adjacent
wall of the orbit.
Insertion.—The fibers passing downward and forward blend with the
fibers of the masseter. Inferiorly it inserts by a tendon to the coranoid
process upon the superior ramal margin of the mandible.
Shape.—Fan-shaped with broad portion uppermost.
Relations.—It occupies the temporal fossa. It is related superiorly with
the dermo-temporalis and skin. Inferiorly, with the biventer maxillæ and the
masseter.
Action.—It aids in closing the jaw.
Masseter (Fig. 19, No. 1). Location.—Occupies the supero-lateral
portion of the surface of the lower jaw.
Origin.—In two portions: the first, by a broad and thin tendon from the
entire length of the bony ridge above the external auditory meatus, from the
squamosal process, and from the outer portion of the quadrate bone; the
second, from the side and under border of the zygoma.
Insertion.—The first portion: The fibers pass downward and forward
beneath the zygoma; a few of the fibers blend with those of the temporal;
one tendon inserts to a small tubercle on the upper border of the jaw behind

the coronoid process, and by fleshy insertion to the outer side of the ramus
of the lower jaw, quite as far forward as the horny portion of the beak. The
second portion: by a small tendon to the mandible on its upper border
immediately in front of the articular portion.
Shape.—Flat, and elongate. Somewhat fleshy.
Relations.—Superiorly with the temporal, and inferiorly with the
biventer maxillæ and stylo-hyoideus. Externally with the skin, and
internally with the jaw bone.
Action.—Aids in closing the jaw.
Biventer Maxillæ (Fig. 19, No. 3). Location.—Covers the outer
posterior portion of the mandible.
Origin.—It arises in two portions: The first, from a ridge bounding the
posterior part of the auditory canal; the second, from a depression of the
mesial side. These two parts blend and extend downward and forward.
Insertion.—To the posterior part of the articular end of the mandible.
Shape.—A curved fleshy mass.
Relations.—Superiorly with the temporal and stylo-hyoideus. Posteriorly
with the digastricus and genio-hyoideus. Internally with the jaw bone, and
externally with the skin.
Action.—It aids in opening the jaw.
Entotympanic. Location.—Posterior to the pterygoid.
Origin.—From the side of the basi-sphenoid and from the base of the
rostrum immediately beyond it.
Insertion.—The fibers pass downward and forward, and insert by a
double tendinous slip. One slip inserts to a spine-like process on the upper
side of the pterygoid, and the other to the quadrato-pterygoidean
articulation.
Shape.—Spindle-shaped.
Relations.—Anteriorly with the pterygoid. Internally and posteriorly with
the basi-sphenoid. Externally with the pterygoideus internus.
Action.—Aids in raising the upper mandible by pulling forward the
quadratus and pterygoidean against the palatines.
Pterygoideus Internus (Fig. 17, No. B, 5). (Synonym.—Pterygoideus
medialis.[4])

4. According to international veterinary nomenclature.

Location.—A muscular mass at the roof of the mouth.
Origin.—From the major part of the surface of the palatine bone and the
distal head and shaft of the pterygoid and the sphenoidal projection.
Insertion.—By a tendon to the antero-internal part of the articular part of
the mandible.
Shape.—Fusiform with a thick fleshy belly.
Relations.—Superiorly with the palatine, the pterygoid, and the sphenoid
bones. Inferiorly with the skin.
Action.—It aids in closing the jaw.
Pterygoideus Externus. (Synonym.—Pterygoideus lateralis.)
Location.—Supero-external to the pterygoideus internus.
Origin.—From the outer part of the extremity of the orbital process of the
quadrate.
Insertion.—The fibers pass downward, outward and forward and are
inserted to the inner part of the mandibular ramus.
Shape.—A small round bundle.
Relations.—Inferiorly with the pterygoideus internus. Externally with the
inferior maxilla.
Action.—Aids in closing the jaw.
Digastricus (Fig. 17, No. B, 16). Location.—Extends from the basi-
temporal to the side of the neck.
Origin.—From the external lateral angle of the basi-temporal.
Insertion.—Opposite the angle of the jaw the fibers spread out in fan-like
arrangement. The muscle meets its fellow of the opposite side; extends
longitudinally over the superior larynx, for some distance down the neck.
Shape.—Thin and ribbon-shaped.
Relations.—Externally to the platysma myoides. The anterior fasciculi
blend with those of the mylo-hyoideus; internally with the larynx at the
upper part.
Action.—To raise the trachea and hyoid apparatus against the pharynx.

THE MUSCLES OF THE TONGUE

Mylo-hyoideus
Stylo-hyoideus
Genio-hyoideus
Cerato-hyoideus
Sterno-hyoideus
Depressor-glossus
Cerato-glossus
Hyoideus transversus

Mylo-hyoideus. Location.—The forepart of the inter-ramal space.
Origin.—From the inner side of the lower jaw at a point just above the
lower border and the inturned edge of the horny sheath of the beak.
Insertion.—By aponeurosis to the under side of the hyoid, on the median
line between the first and the second basi-branchial.
Shape.—Thin, flat, and delicate.
Relations.—Inferiorly with the skin. Thin and rather broad, it meets its
fellow of the opposite side. Laterally with the rami of the jaw. Superiorly
with the hyoid apparatus.
Action.—Lifts the tongue upward against the roof of the mouth.
Stylo-hyoideus (Fig. 17, No. B, 6). Location.—Supero-posterior to the
hyoid apparatus.
Origin.—From the outer portion of the articular enlargement of the lower
jaw.
Insertion.—By a tendon to the basi-branchial of the thyro-hyal.
Shape.—A long transversely flattened fasciculus.
Relations.—Supero-posterior part of the hyoid apparatus along side the
genio-hyoideus and the cerato-hyoideus.
Action.—Singly, pulls the tongue to one side; acting with its fellow, pulls
the tongue upward.
Genio-hyoideus (Fig. 9, No. 7). Location.—Supero-posterior to the
hyoid apparatus.
Origin.—From the anterior portion of the inner side of the lower jaw.

Insertion.—To the middle of the outer side of the basi-branchial of the
corner of the os hyoides which cornu it completely envelops.
Shape.—A long, rather thick fasciculus.
Relations.—With the stylo-hyoideus and cerato-hyoideus.
Action.—Protrudes the tongue from the mouth.
Cerato-hyoideus (Fig. 9, No. 8). (Synonym.—Kerato-hyoideus.)
Location.—Inferior to the hyoid apparatus.
Origin.—By a delicate tendinous slip from the under side of the shaft of
the basi-hyal element of the hyoid apparatus.
Insertion.—To a small elevation on the under side of the anterior end of
the glosso-hyal.
Shape.—A small round muscular fasciculus becoming tendinous in its
anterior half.
Relations.—Superiorly with the hyoid apparatus.
Action.—Singly, pulls the tongue to one side; acting with its fellow,
depresses the tongue.
Sterno-hyoideus. Location.—Inferior to the hyoid apparatus.
Origin.—From the outer anterior surface of the thyroid bone of the
superior larynx.
Insertion.—To the anterior part of the basi-hyal.
Shape.—At first broad and rather fleshy, becomes contracted and
somewhat tendinous.
Relations.—Inferior to the hyoid apparatus and superior larynx.
Action.—When the larynx is fixed, acting alone deflects the tongue
laterally; acting with its fellow, depresses the tongue. If the base of the
tongue is fixed the two pull the larynx forward. Hence muscles of
deglutition.
Depressor-glossus. Location.—Superior to the basi-hyal.
Origin.—From the under portion of the basi-hyal.
Insertion.—To under part of the glosso-hyal.
Shape.—Small, short.
Relations.—Superiorly with the basi-hyal and glosso-hyal bones.

Action.—Depresses the tip of the tongue and elevates the base.
Cerato-glossus. Location.—On the upper portion of the cornu of the
hyoid.
Origin.—One-half of the surface of the first basi-branchial.
Insertion.—To the upper side of the shaft of the cerato-branchial element
of the hyoid apparatus.
Shape.—A small muscular fasciculus.
Relations.—Supero-laterally to the cerato-branchial element.
Action.—Elevates the cornua of the hyoid arches and presses them
against the skull.
Hyoideus Transversus (Fig. 9, No. 9 and 10). Location.—Envelops the
spur process of the euro-hyal.
Origin and Insertion.—It extends from the inner side of one cornu to the
spur process.
Shape.—Thin, flat.
Relations.—Posterior to the euro-hyal, which it envelops, and between
the cornua of the os hyoides.
Action.—Approximates the cornua of the os hyoides.

THE CERVICAL MUSCLES

Complexus
Rectus capitis anticus minor
Flexor capitis inferior
Rectus capitis posticus major
Biventer cervicis
Longus colli posticus
Obliquus colli
Longus colli anterior
Rectus capitis lateralis
Trachelo-mastoideus
Interspinales
Interarticulares
Obliquo-transversales

Intertransversales
Scalenus medius
Complexus (Fig. 19, No. 5). Location.—Supero-lateral portion of the
neck.
Origin.—By three tendinous slips from the antero-lateral portion of the
transverse process of the fourth, the fifth, and the sixth cervical vertebræ.
Insertion.—The muscular fibers pass around the neck and meet their
fellows in the median line in a fascia formation. The thin tendinous sheet
inserts into the occiput just above the occipital ridge.
Shape.—From point of origin this muscle expands into a broad sheet.
Relations.—It overlies the muscles of the occipital region.
Action.—It extends the head.
Rectus Capitis Anticus Minor (Fig. 19, No. 8). (Synonym.—Rectus
capitis ventralis minor.)
Location.—Infero-lateral portion of the neck.
Origin.—From the apices of the hyapophyses of the second, the third,
and the fourth cervical vertebræ.
Insertion.—To the occiput just below the complexus.
Shape.—A long and rather thick fasciculus.
Relations.—Externally with the skin. The tendinous slips of origin pass
between the flexor capitis inferior and longus colli anterior.
Action.—Extends the head.
Flexor Capitis Inferior (Fig. 19, No. 7). Location.—Antero-inferior part
of the neck.
Origin.—From the apices of the hyapophyses of the second, the third,
and the fourth cervical vertebræ.
Insertion.—To the triangular area on the basi-temporal of the base of the
cranium.
Shape.—At first tendinous, becomes somewhat fleshy as it passes
forward.

Fig. 19.—Muscles of the head and neck. 1, Masseter muscle. 2, Infraorbital
sinus. 3, Biventer maxilla. 4, Temporalis. 5, Complexus. 6, Rectus capitis
posticus major. 7, Flexor capitis inferior. 8, Rectus capitis anticus minor. 9,
Biventer cervicis. 10, Longus colli posticus. 11, Obliquus colli. 12,
Intertransversales. 13, Longus colli anterior. 14, Lateral temporo-maxillary
ligament. 15, Lateral ligament of the jaw. 16, Trachelo-mastoideus. 17, Rectus
capitis lateralis. 18, Scalenus medius. 19, Rhomboideus. 20, Trapezius. 21,
Location of scapula. 22, Supraspinatus. 23, Teres et Infraspinatus.

Relations.—Antero-inferior portion of the neck close to the rectus capitis
anticus minor.
Action.—Flexes the head upon the neck.
Rectus Capitis Posticus Major (Fig. 19, No. 6). (Synonym.—Rectus
capitis dorsalis major.)
Location.—Supero-lateral area on the anterior portion of the neck.
Origin.—From the median anterior aspect of the second cervical
vertebra, and the supero-anterior border of the neural canal.
Insertion.—To the crescent-shaped area at the back of the skull.
Shape.—Short, thick, fleshy bundle.
Relations.—Superiorly with the complexus; inferiorly with the trachelo-
mastoideus and the vertebræ.
Action.—Singly, pulls the head to one side; acting with its fellow, extends
the head.

Biventer Cervicis (Fig. 19, No. 9). Location.—Occupies the superior
part of the neck.
Origin.—From the side of the neural spine of the first dorsal vertebra,
and from the adjacent tendon of the longus colli posticus.
Insertion.—To the occiput.
Shape.—Tendinous in the middle with a more or less spindle-shaped
belly at each end.
Relations.—Superior to the longus colli posticus. It lies next to the skin.
Action.—Extends the head on the neck and elevates the neck.
Longus Colli Posticus (Fig. 19, No. 10). (Synonym.—Longus colli
dorsalis.)
Location.—Occupies the superior part of the neck.
Origin.—From the marginal edges of the summits of the neural spines of
the first two dorsal vertebræ.
Insertion.—To the transverse process of the axis, and superior part of the
cervical vertebræ.
Shape.—A long, somewhat narrow, flattened muscle, the inferior portion
of which is divided into five or six fasciculi.
Relations.—Superiorly with the biventer cervicis and inferiorly with the
vertebræ.
Action.—Raises the neck upward.
Obliquus Colli (Fig. 19, No. 11). Location.—On the lateral side of the
neck.
Origin and Insertion.—The first of the seven fasciculi originates from the
diapophysis of the eleventh cervical vertebra, winds obliquely over the
tenth, and is inserted into the posterior margin of the postzygapophysis of
the ninth vertebra. In its passage it receives the slip from the longus colli
posticus. The next fasciculus originates from the transverse process of the
tenth cervical vertebra, winds obliquely over the ninth vertebra, and is
inserted to the postzygapophysis of the eighth vertebra. In its passage it also
receives a fasciculus from the longus colli posticus. The next three fasciculi
originate in a similar manner being attached to similar postzygapophyses
and have slips extending forward which slips are inserted to the neural
spines of the alternate vertebræ. The sixth fasciculus originates from the

transverse process of the sixth vertebra, passing obliquely up the neck is
inserted to the extremity of the diapophysis of the fourth vertebra, the outer
extremity of the transverse process of the third vertebra. The seventh, or
anterior, fasciculus originates from the transverse process of the fifth
vertebra, and is inserted to the extremity of the diapophysis of the third
vertebra.
Shape.—Short, thick fasciculi.
Relations.—Laterally with the vertebræ. Inferiorly with the
intertransversales. Superiorly with the longus colli posticus, and externally
with the skin.
Action.—Flexes one vertebra on the other laterally.
Longus Colli Anterior (Fig. 19, No. 13). (Synonym.—Longus colli
ventralis.)
Location.—Occupies the anterior portion of the neck.
Origin and Insertion.—This muscle is divided into a vertical portion, and
a superior and an inferior oblique portion. The vertical portion originates
from the hypophyses of the tenth to the fifteenth vertebra and is inserted by
a tendon to the tubercle on the inferior portion of the atlas. Small, slender
tendons are given off and insert to the apices of the parapophyses of the
fourth to the tenth cervical vertebræ. There is more or less attachment to the
bodies of the cervical vertebræ mentioned. The superior oblique portion
originates from the diapophyses of the third, the fourth, the fifth cervical
vertebræ and becoming tendinous is inserted to the tubercle on the inferior
portion of the body of the atlas. The inferior oblique portion originates from
the transverse processes of the fourth, the fifth, and the sixth cervical
vertebræ. It is inserted by a slender tendon to the apex of the parapophysis
of the third cervical vertebra.
Shape.—A long fleshy muscle extending the entire length of the neck.
Relations.—Inferiorly with the skin and superiorly with the cervical
vertebræ.
Action.—Pulls the neck downward.
Rectus Capitis Lateralis (Fig. 19, No. 17). Location.—The infero-
lateral anterior portion of the neck.
Origin.—Originates tendinous from the diapophysis of the third, the
fourth, and the fifth cervical vertebræ.

Insertion.—Passes obliquely upward in front of the spinal column to the
inner tubercle on the basal ridge of the basi-temporal bone, by a
subcompressed tendon.
Shape.—A somewhat thick fasciculus.
Relations.—Superiorly with the trachelo-mastoideus, inferiorly with the
longus colli anterior, and externally with the skin.
Action.—Singly, pulls the head down and to one side; acting with its
fellow, pulls the head downward.
Trachelo-mastoideus (Fig. 19, No. 16). (Synonym.—Longissimus
capitis et atlantis.)
Location.—Laterally on the anterior portion of the neck.
Origin.—Semitendinous from the diapophyses of the second, the third,
the fourth, and the fifth cervical vertebræ.
Insertion.—By subcompressed tendon to the base of the cranium, at the
outer tubercle of the basal ridge of the basi-temporal.
Shape.—Flattened from side to side; broad at the posterior portion,
becomes angular at the anterior portion.
Action.—Singly, pulls the head down and to one side; acting with its
fellow, pulls the head downward.
Interspinales (Fig. 17, A, No. 2). Location.—Superior to the vertebra.
Origin and Insertion.—A series of muscles connecting the superior
neural spines of the cervical vertebræ.
Shape.—Thin, flat.
Relations.—Anteriorly the posterior border of the vertebræ in front and
posteriorly the anterior border of the succeeding vertebræ, inferiorly by the
vertebræ.
Action.—To approximate the spinous portion of the vertebræ.
Interarticulares (Fig. 17, No. A, 4). Location.—Supero-laterally to the
vertebræ. Between the postzygapophysis.
Origin and Insertion.—From the posterior margin of the ring of the atlas
to the postzygapophysis of the axis. Then in the succeeding vertebræ from
the postzygapophysis of the vertebra to the same of the succeeding vertebra.
Shape.—Muscular bundle.

Relations.—Inferiorly with the vertebræ. Supero-laterally with the
obliquo-transversales.
Action.—Aids in approximating the vertebræ in a supero-lateral
direction.
Obliquo-transversales (Fig. 17, A, No. 1). Location.—Supero-lateral to
the vertebræ.
Origin and Insertion.—Passes obliquely from the transverse process of
one vertebra to the postzygapophysis of the vertebra beyond.
Shape.—A thin fasciculus.
Relations.—Inferiorly with the interarticulares and laterally with the
intertransversales.
Action.—Aids in flexing the vertebræ supero-laterally.
Intertransversales (Fig. 19, No. 12). Location.—Laterally to the
vertebræ.
Origin and Insertion.—Extend between the transverse processes
beginning at the third cervical vertebra.
Shape.—Short, thick.
Relations.—Laterally the vertebræ. Superiorly the obliquo-transversales.
Action.—Aids in flexing the vertebræ laterally.
Scalenus Medius (Fig. 19, No. 18). (Synonym.—Scalenus.)
Location.—Supero-laterally to the entrance of the thorax.
Origin.—From the diapophysis and pleurapophysis of the eleventh
cervical vertebra.
Insertion.—To the entire border of the first rib. A few fibers pass over to
the anterior free margin of the middle third of the second rib.
Shape.—Rather pyramidal in shape with base uppermost.
Relations.—Posteriorly with the levatores costarum. Internally with the
longus colli.
Action.—When the first rib is fixed singly, turns the neck to one side;
acting with its fellow, extends the neck. When the neck is fixed, by drawing
the first rib forward, it acts as an inspiratory muscle.

THE MUSCLES OF THE AIR PASSAGES

The Superior Larynx

Constrictor glottidis
Thyreo-arytenoideus

The Inferior Larynx

Tracheo-lateralis
Broncho-trachealis posticus
Broncho-trachealis anticus
Broncho-trachealis brevis
Bronchialis posticus
Bronchialis anticus
Sterno-trachealis

Constrictor Glottidis. Location.—Supero-anterior portion of the
superior larynx.
Origin.—From the superior and longitudinal line of the thyroid plate.
Insertion.—All along the inner margin of the arytenoid bone, and to the
apex of the mid-cricoidal segment.
Shape.—Thin, flat sheet extending outward and upward, and then
inward.
Relation.—Interiorly with the larynx.
Action.—The two muscles of this kind acting together, close the glottis
by drawing the apices of the arytenoids to the median line.
Thyreo-arytenoideus. Location.—Supero-lateral portion of the superior
larynx.
Origin.—From the entire outer margin of the thyroid plate and the outer
margin of the cricoid bone.
Insertion.—All along the outer margin of the arytenoid bone and the
outer border of the central cricoid piece.
Shape.—A thin, flat sheet.
Relations.—Infero-laterally with the superior larynx.

Action.—The two muscles of this kind acting together, open the glottis
by pulling the arytenoid bone outward.
Tracheo-lateralis (Fig. 20, No. 2). Location.—Along the lateral side of
the trachea.
Origin.—By the union of the bronchio-trachealis posticus and bronchio-
trachealis anticus, on the lateral side of the trachea, about 1½ centimeters
from the bifurcation of the trachea.
Insertion.—In delicate fan-like structure to the side of the trachea, near
the superior larynx.
Shape.—Thin, ribbon-shaped, closely attached to the trachea.
Relations.—Internally with the trachea, and externally with the skin and
other integument.
Action.—Acts as a brace to the sides of the trachea, and contracting,
approximates the tracheal rings and thus shortens the trachea.
Broncho-trachealis Posticus (Fig. 21, No. 3). Location.—Postero-
superior portion of the trachea. The fibers pass downward and backward.
Origin.—From the inferior end of the tracheo-lateralis.
Insertion.—To the end of the third half of the bronchial ring of the same
side.
Shape.—A small fasciculus.
Relations.—Internally with the trachea, and externally with the skin and
other integument.

Fig. 20.—The anterior pectoral region. 1, Sterno-trachealis. 2, Tracheo-lateralis.
3, Broncho-trachealis brevis. 4, Costal process of sternum. 5, Right and left
carotid converging and occupying same sheath at 6. 7, The heart showing
branches of coronary artery. 8, Cervical air-sac. 9, Left brachio-cephalic artery.
10, Right brachio-cephalic artery. 11, Trachea. 12, Inferior larynx. 13.
Subclavian artery. 14, Carotid trunk. 15, Internal thoracic artery. 16 Thyroid
gland. 17, Anterior vena cava. 18, Auricular appendage.

Fig. 21.—The inferior tracheal region.
1, Bronchialis anticus. 2, Bronchialis
posticus. 3, Broncho-trachealis posticus.
4, Broncho-trachealis anticus.

Action.—A tensor of the true or inferior larynx.
Broncho-trachealis Anticus (Fig. 21, No. 4). Location.—Anterior
portion of the inferior extremity of the trachea.
Origin.—The anterior branch of the bifurcated tracheo-lateralis.
Insertion.—To the anterior extremity of the third half ring of the
bronchus of the same side.
Shape.—A small fasciculus.
Relations.—Internally with the trachea, and externally with the skin and
other integument.
Action.—A tensor of the inferior larynx.
Broncho-trachealis Brevis (Fig. 20, No. 3). Location.—Posterior part of
the inferior extremity of the trachea.
Origin.—From just beneath the broncho-trachealis anticus muscle.
Insertion.—Extends obliquely across the inferior larynx and is inserted to
the posterior end of the second bronchial ring.
Shape.—Rather short, strong, straight, subcylindrical.
Relations.—Internally with the trachea, and laterally with the broncho-
trachealis posticus.
Action.—A tensor of the inferior larynx.
Bronchialis Posticus (Fig. 21, No. 2). Location.—Supero-lateral side of
the anterior end of the bronchi.
Origin.—From the lateral inferior margin of the last tracheal ring.
Insertion.—Passing obliquely across the larynx it inserts to the posterior
extremity of the second half ring of the bronchus.
Shape.—Small, thick, spindle-shaped.
Relations.—Internally with the trachea, inferiorly with the bronchialis
anticus, and superiorly with the broncho-trachealis brevis.
Action.—A tensor of the larynx.
Bronchialis Anticus (Fig. 21, No. 1). Location.—Inferior to the former
muscle.
Origin.—From the last ring of the trachea.
Insertion.—The fibers pass obliquely forward and become inserted to the
rim of the arytenoid cartilage of the inferior larynx, and the anterior

extremities of the first and second half rings of the bronchus.
Shape.—Thick, spindle-shaped; about twice the size of the bronchialis
posticus.
Relations.—It is crossed at its origin by the broncho-trachealis anticus
and is related internally with the bronchus and end of the trachea.
Action.—A tensor of the larynx.
Sterno-trachealis (Fig. 20, No. 1). Location.—The inferior region of the
trachea above the above-named muscles.
Origin.—From the side of the trachea beneath the posterior border of the
broncho-trachealis anticus.
Insertion.—Passes downward and backward across the cavity of the
chest and is inserted to the inner part of the costal process of the sternum.
Shape.—A delicate cord of fibers.
Relations.—Internally with the broncho-trachealis muscles.
Action.—A relaxor of the larynx, and hence, of the tympanic membrane.

THE STERNAL GROUP

Triangularis Sterni. Location.—In the floor of the thoracic cavity.
Origin.—From the entire superior margin of the summits of the costal
processes.
Insertion.—The fibers extend upward and backward, dividing into four
digitations which cover the inner surface of the three principal sternal ribs,
and are inserted to the first four as high as their articulations with the
vertebral ribs.
Shape.—Flat and somewhat triangular.
Relations.—Interiorly with the floor of the thoracic cavity.
Action.—A powerful muscle of expiration. In contracting, lessens the
cubic content of the thorax.
The Diaphragm (Fig. 47, No. 10; Fig. 33, No. 9). Description.—The
diaphragm in the domestic fowl is rudimentary. It consists of a thin semi-
transparent membrane, situated between and separating the thoracic and the
abdominal cavities. It readily conforms to the various organs pressing upon

it from each side. On each side are three rudimentary muscles which extend
from the vertebral heads of the second, the third, and the fourth sternal ribs.
The fibers of these muscles spread out in fan-like upon the diaphragm, and
are seen just above the digitations of the triangularis sterni.

THE ABDOMINAL MUSCLES

Obliquus abdominis externus
Obliquus abdominis internus
Rectus abdominis
Transversalis abdominis

Obliquus Abdominis Externus (Fig. 22, No. 1). Location.—The
outermost muscle of the lateral abdominal wall.
Attachments.—By a delicate aponeurotic membrane, from the sides of all
the true dorsal ribs, from the posterior border of the last vertebral rib and
the adjoining margins of the pelvis, and from the entire posterior surface of
the inferior border of the post-pubic element of the pelvis; by aponeurosis,
blending with the fascia toward the root of the tail and lower part of the
abdomen; and by aponeurosis to the sides of the sternum, to the under part
of the pectoralis major muscle, and to the zyphoid prolongation. Also by
aponeurosis it meets its fellow from the opposite side, at the linea alba.

Fig. 22.—The abdominal muscles of a hen. Right side. 1, Obliquus abdominis
externus. 2, Obliquus abdominis internus. 3, Peritoneum covering intestines. 4,
Peritoneum covering the gizzard. 5, The lungs (note how small they are from a
relative standpoint). 6, The great sciatic or ischiadic nerve. 7, Lumbar nerves. 8,
Kidney. 9, Brachial plexus. 10, Pericardium of the base of the heart. 11, Anterior
vena cava. 12, Oil gland. 13, Showing a sacculation of the abdominal muscles.
There is no tunica abdominalis in the fowl.

Obliquus Abdominis Internus (Fig. 22, No. 2). Location.—Just internal
with regard to the external oblique.
Attachments.—By aponeurosis, from the posterior third of the post-pubic
element of the pelvis; by muscular fibers, from the balance of the bone; and
by a few fibers, from the iliac border posterior to the acetabulum.
Anteriorly, these fibers are inserted to the entire posterior margin of the last
vertebral rib, and into the pleurapophysial head of the last costal rib.
Rectus Abdominis (Fig. 13, No. 10 and Fig. 23, No. 1). Location.—The
inferior median abdominal wall.
Attachments.—By aponeurosis, from the distal extremity of the post-
pubic element of the pelvis and from the semitendinous ligament which
stretches from one post-pubic tip to the other. Attaches anteriorly to the
zyphoid margin of the sternum, and passes, by a broad aponeurotic
membrane, over the outer surface of the thoracic wall beneath the external
oblique.
Transversalis Abdominis (Fig. 25, No. H, 1). Location.—Infero-lateral
portion of the abdominal wall.
Attachments.—By a thin, tendinous attachment from the entire post-
pubic and iliac margins of the pelvis and from the interpubic ligament. Its

fibers cross the abdomen between the peritoneum, the rectum, and the
internal oblique. It is inserted over the entire pleural part of the last two
vertebral ribs, the intercostal muscles between them, and the same surface
of the hemapophyses connected below. Inserts into the linea alba.
Action.—The abdominal muscles give support to the abdominal organs,
aid in flexing the spine, draw the last rib backward, thus aiding in
respiration, and compress the abdominal organs to aid in defecation and
expiration.

THE DORSO-LUMBAR REGION

Sacro-lumbalis
Longissimus dorsi

Sacro-lumbalis. Location.—The lateral lumbo-sacral region.
Origin.—Tendinous from the anterior margin of the ilium, from the
angles of the last two vertebral ribs, and by tendinous slips, from the outer
ends of the transverse processes of the last three dorsal vertebræ.
Insertion.—By a few fleshy fibers into the angle of the first dorsal rib
and to the corresponding points upon the free cervical ribs, and by a strong
semitendinous insertion into the outer extremity of the diapophysis of the
twelfth cervical vertebra.
Shape.—A close fitting, tendo-muscular sheet extending between the
anterior margin of the ilium and the root of the neck.
Relations.—Intimately blended with the longissimus dorsi externally.
Action.—Assists the longissimus dorsi.
Longissimus Dorsi (Fig. 24, No. 4). Location.—The superior dorso-
lumbar region.
Origin.—From the inner portion of the anterior margin of the ilium, and
from the various surfaces afforded by its walls and the walls of the ilio-
neural canal; by a series of short and distinct tendons alternately from the
anterior and posterior extremities of the summits of the neural spines of all
the dorsal vertebræ. From the diapophyses of the dorsal vertebræ, from the
crests of the neural spines of the last three dorsal vertebræ, from the bodies
of the dorsal vertebræ, and from the fascia between them and the sacro-

lumbalis; and also by a tendinous sheet continuous with the origin of the
longus colli posticus.
Insertion.—By four fasciculi into the free posterior margins of the
oblique processes of the eleventh, the twelfth, the thirteenth, and the
fourteenth cervical vertebræ.
Shape.—A large flat sheet.
Relations.—Laterally, with the superior spinous processes of the
vertebræ, and with the superior surface of the ribs.
Action.—Singly, flexes the back laterally; with its fellow, aids in
elevating the body upward.

THE COCCYGEAL MUSCLES

Levator coccygis
Levator caudæ
Transversus peronei
Depressor caudæ
Depressor coccygis
Lateralis caudæ
Lateralis coccygis
Infracoccygis

Levator Coccygis (Fig. 23, No. 2). Location.—The superior part of the
caudal apparatus.
Origin.—From a limited area of the ilium just beyond and to the side of
the anterior free caudal vertebræ.
Insertion.—Into the tuberosity of the anterior margin of the pygostyle.
Shape.—Short, fleshy.
Relations.—Superior portion of the coccygeal vertebræ.
Action.—Elevates the tail.
Levator Caudæ (Fig. 23, No. 4). Location.—Supero-lateral side of the
tail.
Origin.—From the posterior surface of the post-acetabular area of the
pelvis, and from the superior surface of all the coccygeal vertebræ except

the pygostyle.
Insertion.—To the four inner quill butts of the main tail feathers.
Shape.—Long, spindle-shaped.
Relations.—Internally, with the levator coccygis and externally, with the
lateralis caudæ.
Action.—Powerfully elevates the four inner main tail feathers.
Transversus Peronei (Fig. 23, No. 3). Location.—The posterior
abdominal region.

Fig. 23.—Outer layer of muscles of the
tail and thigh, 1, Rectus abdominis. 2,
Levator coccygis. 3, Transversalis
peronie. 4, Levator caudæ. 5, Lateralis
caudæ. 6, Depressor caudæ. 7, Sartorius.
8 and 9, Gluteus primus. 10,
Semitendinosus. 11, Gastrocnemius. 12,
Peroneus longus. 13, Flexor perforatus
indicis secundus pedis. 14, Flexor
perforatus medius secundus pedis. 15,
Lateral ligament of the hock.

Origin.—From the entire posterior margin of the ischium, and from the
posterior margin of the post-pubis extending beyond it.
Insertion.—Becoming aponeurotic, it passes toward the coccyx and is
attached to the entire posterior margin of the ilium. Passes to the median
line, meeting its fellow in front of the anus.
Shape.—Thin, sheet-like.

Relations.—Infero-anteriorly with the anus. Posteriorly with the edges of
the ilium and of the ischium. Internally with the depressor caudæ.
Action.—Gives support to the viscera in the post-anal region, and aids in
attaching the anus to the structures above.
Depressor Caudæ (Fig. 23, No. 6). Location.—The infero-lateral side of
the tail.
Origin.—From the lower half of the posterior border of the ischium, and
from the entire posterior border of the post-pubis beyond.
Insertion.—To the quill butts of the three or four outer main tail feathers.
Shape.—Strong, conical.
Relations.—Externally, with the depressor coccygis.
Action.—Singly, pulls the tail downward and outward; with its fellow,
pulls the tail downward.
Depressor Coccygis. Location.—The outermost of the infero-lateral
muscles of the tail.
Origin.—From the lower half of the posterior margin of the ischium and
the anterior three-fourths of the posterior margin of the post-pubic element
of the pelvis beyond it.
Insertion.—To the thickened rim of the inferior and expanded portion of
the pygostyle.
Shape.—Flat, triangular.
Relations.—Internally with the depressor caudæ.
Action.—Singly, pulls the tail downward and to one side; with its fellow,
pulls the tail downward.
Lateralis Caudæ (Fig. 23, No. 5). Location.—The lateral side of the tail.
Origin.—From the tip of the transverse process of the first free caudal
vertebræ.
Insertion.—To the outer three quill butts of the main tail feathers.
Shape.—Four fasciculi forming a fleshy belly.
Relations.—Inferiorly, with the levator caudæ and superiorly with the
depressor caudæ.
Action.—Singly, pulls the tail downward and outward; with its fellow,
pulls the tail downward. The outermost fasciculus contracting, spreads the

tail feathers.
Lateralis Coccygis (Fig. 25, No. E, 2). Location.—The infero-lateral
side of the caudal vertebræ.
Origin.—From the surface of the posterior end of the ilium and by
tendons from the under side of the ends of the first three or four caudal
vertebræ.
Insertion.—To the side of the posterior margin of the expanded portion of
the pygostyle.
Shape.—Subcompressed mass.
Relations.—With the transverse processes of the caudal vertebra,
inferiorly.
Action.—Controls the lateral movements of the tail and its feathers, and
the oblique downward movement.
Infracoccygis (Fig. 25, No. E, 1). Location.—The extreme inferior
portion of the caudal vertebræ.
Origin.—From the inferior surface of the diapophysis of the last vertebra
which anchyloses with the pelvic sacrum, and from all the free caudal
vertebræ.
Insertion.—Into the lower side of the pygostyle.
Shape.—Flat, somewhat triangular.
Relations.—Superiorly, with the vertebræ, laterally, with the lateralis
coccygis, and mesially, with its fellow of the opposite side.
Action.—Depresses the tail.

THE COSTAL REGION

Latissimus dorsi
Trapezius
Rhomboideus
Serratus magnus anticus
Serratus parvus anticus
Teres et infraspinatus
Intercostales
Levatores costarum

Appendico-costales
Latissimus Dorsi (Fig. 24, No. 7). Location.—Supero-lateral portion of
the dorsal region.
Origin.—From two portions, the anterior slip from the outer edge of the
superior margins of the neural spines of the second and the third dorsal
vertebræ, and the second portion from a similar point on all the succeeding
dorsal vertebræ. The second portion is fascia-like in its attachments.
Insertion.—The fibers converge toward the humerus and enter between
the deltoid the scapular head of the triceps and the remaining heads of this
muscle and is inserted to the anconal part of the humerus, just within in the
radial crest.
Shape.—Thin, triangular.
Relations.—Superiorly, with the skin. The most superficial of the dorsal
muscles.
Action.—To elevate the humerus and thus flex the shoulder-joint. An
expiratory muscle when the wing is fixed.
Trapezius (Fig. 19, No. 20). Location.—In the shoulder region, just
below the longissimus dorsi.
Origin.—From the neural spines of the second, the third, the fourth, and
the fifth cervical vertebræ just below the latissimus dorsi.
Insertion.—To the mesian upper border of the scapula.
Shape.—A flat oblong layer of fibers.
Relations.—The posterior part of the trapezius overlies the anterior part
of the rhomboideus. The posterior two-thirds is covered by the latissimus
dorsi. The anterior third is superficial.
Action.—Draws the scapula forward.
Rhomboideus (Fig. 19, No. 19). Location.—Supero-posterior scapular
region.
Origin.—From the neural spines of the first four dorsal vertebræ beneath
the latissimus dorsi and trapezius muscles.
Insertion.—The fibers passing outward and backward attach to the
posterior third of the mesial or upper border of the scapula.
Shape.—Thin, flat, delicate.

Relations.—Superiorly, by the latissimus dorsi and the trapezius.
Action.—To draw the free end of the scapula upward and forward.
Serratus Magnus Anticus (Fig. 13, No. 16). Location.—The supero-
lateral side of the thorax.
Origin.—By three strong digitations: first, from the outer part of the
second true rib just above the base of the epineural appendage; the other
two, from similar locations on the two succeeding ribs, just above the origin
of the dermo-ulnaris.
Insertions.—The first by tendinous attachment to the
interpleurapophysial membrane. The rest of the fibers pass upward and
slightly forward, and are inserted to the inferior surface of the apex of the
scapula.
Shape.—Three flat, strong digitations.
Relations.—Internally, with the ribs.
Action.—If the scapula is fixed, it is a muscle of inspiration.
Serratus Parvus Anticus. Location.—The outer and upper surface of the
anterior part of the thorax.
Origin.—By three digitations from the outer surface of the first three ribs
above the origin of the serratus magnus anticus and the thoraco-scapularis.
Insertion.—The thin sheet of fibers passes upward and backward, and is
inserted to the inferior margin of the scapula.
Shape.—Thin, flat.
Relations.—Internally, with the ribs.
Action.—If the scapula is fixed, it is a muscle of respiration.
Teres et Infraspinatus (Fig. 13, No. 11). Location.—Scapular region.
Origin.—From the superior surface and outer margin of the posterior
two-thirds of the scapula.
Insertion.—The fibers pass forward and outward, and insert to the
humerus at the middle of the ulnar margin of the pneumatic fossa, between
the forks of the triceps.
Shape. —Flat, triangular-shaped.
Relations.—Anteriorly, with the supraspinatus. Internally, with the ribs.

Action.—Aids in keeping the humerus in its socket. Assists in closing the
wing by drawing the humerus to the side of the body.
Intercostales (Fig. 24, No. 5). Location.—Between the ribs of the upper
thoracic region.
Origin and Insertion.—From the anterior border of one rib, the fibers,
passing obliquely upward and forward, and the lower portion downward
and forward, are inserted to the posterior border of the rib just in front.
Shape.—They are best developed in the anterior portion of the thoracic
region and extend down as far as the sternal ribs.
Relations.—Internally the pleura, and anteriorly and posteriorly the ribs.
Action.—The first rib being rendered fixed by the scalenus medius, the
muscles draw the ribs forward, thus aiding inspiration.
Levatores Costarum (Fig. 24, No. 2). Location.—Supero-lateral portion
of the thorax.
Origin and Insertion.—A series of muscles, the first of which extends
from the extremity of the transverse process of the twelfth vertebra, the
fibers passing downward and backward to the anterior free margin of the
upper third of the long posterior rib, and to the external surface close to its
margin. The others arise and insert in a similar manner from the ends of the
diapophyses of all the dorsal vertebræ and attach to each succeeding rib.
Those in front are best developed.
Shape.—Thin and triangular.
Relations.—External to the intercostales.
Action.—Aids in respiration.
Appendico-costales (Fig. 24, No. 1). Location.—The lateral side of the
thorax.
Origin and Insertion.—From the posterior edge of an uncinate process or
epineural appendage, the fibers extending downward and backward to the
outer surface of the succeeding rib.
Shape.—A series of thin triangular-shaped muscles.
Relations.—Internally, with the intercostales.
Action.—Aids in respiration.

THE ANTERIOR PECTORAL GROUP

Tensor patagii longus
Tensor patagii brevis

Tensor Patagii Longus (Fig. 15C, No. 1; Fig. 14, No. 2). Location.—
Anterior shoulder region, in the triangular patagium of the wing.
Origin.—By a flat tendon common to it and the tensor patagii brevis
from the supero-mesial line of the head of the clavicle.
Insertion.—By a long slender tendon extending in the duplicature of the
patagium, with which the fibers blend. Passing to the side of the extensor
metacarpi radialis longus, it extends over the end of the radius and is
inserted to the os carpi radiale, and to the fascia which binds down the other
tendons on the anterior part of the wrist-joint.
Shape.—Cone-shaped belly terminating in a long tendon.
Relations.—Externally, with the skin; by its tendon, with the border of
the extensor metacarpi radialis longior.
Action.—Tenses the soft part in the fold of the wing, and aids in flexing
the forearm.
Tensor Patagii Brevis (Fig. 14, No. 3). Location.—In the triangular
patagium of the wing.
Origin.—From the head of the clavicle in common with the preceding.
Insertion.—The tendon bifurcates, one branch blending with the fascia of
the extensor metacarpi radialis longior, the other inserting just below the
tubercle on the external condyle of the humerus.
Shape.—Fleshy; somewhat broader and longer than the preceding.
Relations.—Interiorly, with the preceding.
Action.—Assists the tensor patagii longus in flexing the forearm.

THE PECTORAL MUSCLES

Pectoralis major
Pectoralis secundus
Pectoralis tertius

Pectoralis Major (Fig. 13, No. 5). Location.—On the lateral side of the
sternum.
Origin.—From the posterior portion of the lateral wing of the sternal
body, from the outer marginal third of the keel of the sternum, and from the
entire outer side of the limb of the furcula or clavicle.
Insertion.—The fibers converging form toward the proximal third of the
humerus a broad tendon which by its insertion covers the entire palmar part
of the pectoral crest. A few of the tendinous fibers pass over the shoulder-
joint and blend with the long head of the biceps. Near this point it receives
the insertion of the dermo-humeralis.
Relations.—Interiorly, with the skin; superiorly, in the sternal region,
with the pectoralis secundus and the pectoralis tertius.
Shape.—Fleshy; largest of the pectorales.
Action.—Powerfully depresses the humerus. The chief muscle of flight.
Pectoralis Secundus (Fig. 13, No. 9; Fig. 15, No. A, 6). Location.—The
entire lateral side of the sternum.
Origin.—From the anterior sternal extremity of the lower third of the
coracoid, from the keel and sternal wing, and by a tendon from a
membraneous expansion between the coracoid and the clavicular bones and
from the lower third of the coracoid.
Insertion.—The fibers converge into a tendon, which passes upward
around the coracoid to its posterior through a canal formed by the scapula,
the coracoid, and the clavicle, the foramen triosseum (Fig. 15, No. A, 7).
This tendon then passes outward and downward, and becoming flat, inserts
to the humerus just anterior to the radial crest and nearer to the humeral
head than does the pectoralis major.
Relations.—Internally, with the breast-bone; externally, with the
pectoralis major; and superiorly, with the pectoralis tertius.
Shape.—Long, fusiform, fleshy.
Action.—Raises the wing.
Pectoralis Tertius (Fig. 13, No. 6; Fig. 15, No. A, 5). Location.—On the
antero-lateral side of the sternum.
Origin.—From the anterior half of the exterior of the body of the
sternum, from the fascia of the subclavius on the outer border of the costal

process, and from the outer, lower third of the coracoid process.
Insertion.—The fibers pass upward to the outer side of the coracoid, and
becoming tendinous as they reach the humerus, by a strong flattened tendon
insert to the ulnar crest of the humerus on the proximal margin at about a
middle point of the pneumatic fossa.
Relations.—Externally, with the pectoralis major; interiorly, with the
pectoralis secundus; internally, with the fascia of the subclavius and the
sternum.
Shape.—Fleshy, fusiform.
Action.—Assists the pectoralis secundus in elevating the humerus.

MUSCLES OF THE SCAPULAR REGION

Coraco-humeralis
Scapulo-humeralis
Supraspinatus
Subclavius
Coraco-brachialis
Teres minor
Levator scapulæ
Thoraco-scapularis
Subscapularis

Coraco-humeralis. Location.—The scapulo-humeral region.
Origin.—From the outer side of the head of the coracoid, supero-laterally
to the long head of the biceps.
Insertion.—To the palmar part of the head of the humerus just inside of
the insertion of the pectoralis major.
Shape.—A delicate subcylindrical muscle.
Relations.—Superior to the head of the humerus.
Action.—Aids in extending the humerus.
Scapulo-humeralis (Fig. 14, No. 10). Location.—The scapulo-humeral
region.

Origin.—From the inner side of the neck of the scapula just within the
head of the deltoid.
Insertion.—Passing over the top of the shoulder-joint it is inserted to the
palmar part of the humeral head between the insertion of the pectoralis
major and the pectoralis secundus.
Shape.—Narrow, flat ribbon.
Relations.—Along the upper margin of the larger portion of the deltoid.
Action.—Aids in extending the humerus.
Supraspinatus (Fig. 19, No. 22). Location.—Scapular region.
Origin.—From the superior surface and outer third of the scapula.
Insertion.—To the lower border of the pneumatic fossa of the humerus.
Shape.—Thin, flat, triangular.
Relations.—Externally, with the trapezius and posteriorly, with the teres
et infraspinatus.
Action.—If the scapula is the fixed point it will pull the humerus upward
and backward.
Subclavius. Location.—Anterior sternal region.
Origin.—From the entire outer surface of the sternal process of the
sternum and the adjacent outer surfaces of three or four of the
hemapophyses.
Insertion.—To the inferior margin of the coracoid bone, the longer fibers
passing over to the fossa in the lower third of the posterior part of the
coracoid.
Shape.—Rather small, fleshy.
Relations.—Overlapped by the pectoralis tertius.
Action.—Pulls the coracoid outward. Also aids in keeping the coracoid in
place.
Coraco-brachialis (Fig. 13, No. 15). Location.—Along the coracoid
shaft.
Origin.—By a delicate tendon from a small circular point on the postero-
mesial part of the shaft of the coracoid immediately above the attachment of
the subclavius and the fossa at that point.

Insertion.—To the top of the ulnar tuberosity of the humerus. This
subcircular space is common to the teres minor and to this muscle.
Shape.—Long, fusiform.
Relations.—With the shaft of the coracoid between the teres minor and
subscapularis.
Action.—To depress the wing.
Teres Minor (Fig. 13, No. 14). Location.—The coraco-scapular region.
Origin.—From under the side of the anterior tip of the scapula.
Insertion.—Passing outward behind the coracoid head and beneath the
neck of the scapula, it is attached by a small tendon to the top of the ulnar
tuberosity of the humerus in common with the coraco-brachialis, with
which tendon it fuses.
Shape.—Small, chunky.
Relations.—Anteriorly, with the tip of the scapula and behind the
coracoid head. Posteriorly, with the coraco-brachialis.
Action.—Aids in the downward stroke of the wing.
Levator Scapulæ. Location.—Scapular region.
Origin.—By two strong digitations, one from each of the lateral
processes of the first cervical vertebra.
Insertion.—To the middle third of the inferior part of the blade of the
scapula.
Shape.—Small and flat.
Relations.—Inferior to the scapula.
Action.—Pulls the scapula forward, and with it the entire shoulder girdle,
which articulates like a hinge-joint at the costo-sternal juncture.
Thoraco-scapularis. Location.—Lateral side of the chest.
Origin.—From the outer part of the lower half of the first free rib, the
outer side of the next succeeding rib and its epineural appendage, and from
a similar surface on the next rib.
Insertion.—By a broad, flat tendon which passes between the two
divisions of the subscapularis and inserts at a point at the juncture of the
anterior and middle third of the outer margin of the scapula.
Shape.—Broad, flat.

Relations.—Internally, with the ribs and the scapula.
Action.—When the scapula is fixed it is a muscle of inspiration. When
the ribs are fixed, it draws the scapula downward.
Subscapularis. Location.—Scapulo-humeral region.
Origin.—From the anterior and outer half of the scapula.
Insertion.—By a strong and subcylindrical tendon to the top of the ulnar
tuberosity of the humerus close to the combined tendons of the coraco-
brachialis and teres minor.
Shape.—A large and powerful muscle.
Relations.—The flat tendon of the thoraco-scapularis divides the
posterior portion of the belly into two portions.
Action.—A powerful rotary muscle of the head of the humerus; aids in
keeping the humeral head in the glenoid cavity.

THE MUSCLES OF THE BRACHIAL REGION

Biceps
Triceps
Deltoid
Brachialis anticus

Biceps (Fig. 13, No. 8). (Synonym.—Biceps brachii.)
Location.—The anterior brachial region.
Origin.—By a broad tendon it covers the top of the shoulder-joint,
dividing into two heads, giving rise to the long and the short heads. The
long is inserted into the outer part of the head of the coracoid just beyond
the glenoid cavity; the short head to the distal angle of the ulnar tuberosity
of the humerus.
Insertion.—To the ulna just in front of the articular cavity for the
trochlear surface of the distal extremity of the humerus.
Shape.—Large, subfusiform.
Relations.—On one side by the triceps and the other the deltoid and
anteriorly partially covered by the patagii muscles.

Action.—A powerful flexor of the forearm.
Deltoid (Fig. 13, No. 12; Fig. 15, No. 8). Location.—Occupying the
lateral side of the humerus; the brachial region.
Origin.—Divided into two portions, the long narrow head extends from
the clavicular process of the scapula and from the adjacent surface of the
same bone. These fibers then extend around the back of the shoulder-joint,
and are joined by the fibers that arise from the entire outer surface of the
large os humero-scapulare. These latter fibers are inserted upon an
extensive area upon the anconal part of the bone beyond the humeral
articular head, and to almost the entire shaft below it.
Insertion.—By a subcylindrical tendon to the proximal side of the
tubercle of the external condyle, and above the insertion of the extensor
metacarpi radialis longus.
Shape.—Large, fleshy, with tendinous attachment.
Relations.—On one side by the biceps and the other by the triceps also
the patagii.
Action.—To extend the arm.
Triceps (Fig. 15, No. 7). (Synonym.—Triceps brachii.)
Location.—The posterior humeral region.
Origin.—By three portions: by the internal and external heads, and by the
long scapular head. The internal and the external heads are blended except
at their proximal extremities. Each head arises from the anconal surface of
the shaft of the humerus. The internal head being located toward the deltoid
attachment and the external head into the pneumatic fossa. The long head
extends from a circumscribed area just posterior to the glenoid cavity of the
scapula. The fibers pass around the shoulder-joint, beneath the deltoid.
Insertion.—The broad tendon passes over the elbow-joint and is inserted
to the entire under surface of the olecranon of the ulna.
Shape.—Long, large, fleshy.
Relations.—The supraspinatus passes between the internal and the
external heads. It is bounded by the biceps and the deltoid.
Action.—An extensor of the antibrachial region directly antagonizing the
biceps.

Brachialis Anticus (Fig. 15, No. 9; Fig. 14, No. 5). Location.—In the
flexure of the humerus and the ulna.
Origin.—It arises fleshy from a circumscribed area on the inner side of
the anconal part of the distal extremity of the humerus.
Insertion.—The fibers passing directly over the elbow-joint become
inserted to the lateral surface of the proximal end of the ulna close to the
margin of the sigmoid cavity.
Shape.—Small, fleshy.
Relations.—With the joint.
Action.—Assists in flexing the forearm upon the arm. Protects the
structures in the anterior part of the elbow-joint.

THE MUSCLES OF THE FOREARM AND THE HAND

Extensor metacarpi radialis longior
Supinator brevis
Extensor digitorum communis
Pronator brevis
Flexor metacarpi radialis
Extensor ossis metacarpi pollicis
Pronator longus
Extensor indicis longus
Flexor digitorum sublimis
Flexor digitorum profundus
Flexor carpi ulnaris
Flexor carpi ulnaris brevior

Extensor Metacarpi Radialis Longior (Fig. 13, No. 17). Location.—
Superior to the radius.
Origin.—By two strong tendinous heads; the outer from the tubercle of
the external condyle of the humerus, just above the origin of the tendon of
the tensor patagii brevis; the inner and stronger portion from the tubercle
found above the oblique trochlear facet of the distal end of the radius.
Insertion.—Becoming a flat, broad, and strong tendon at about the
middle of the forearm, finally becomes inserted to the apex of the

anchylosed first metacarpal of the carpo-metacarpus.
Shape.—A thick, fusiform belly, tendinous at both extremities.
Relations.—By the side of the pronator brevis.
Action.—Raises the hand, and draws it forward toward the radial margin
of the forearm and retains it on the same side.
Extensor Digitorum Communis (Fig. 15, No. 2). Location.—The upper
metacarpal region.
Origin.—Immediately below the tubercle of the external condyle of the
humerus.
Insertion.—By a small tendon to the outer side of the base of the pollex,
and at a mid-point upon the anterior rim of the proximal phalanx of the
middle finger.
Shape.—Small spindle-shaped, becoming tendinous at about the middle
of the forearm.
Relations.—Occupies the middle of the group of muscles on the outer
side of the forearm.
Action.—An extensor of the digit.
Supinator Brevis (Fig. 14, No. 7). Location.—The superior part of the
radius.
Origin.—From the external condyle of the humerus below the origin of
the tendon of the extensor digitorum communis.
Insertion.—To the outer side of the shaft of the radius, for nearly one-
third of its length.
Shape.—Thin, slender.
Relations.—Inferiorly, with the bone.
Action.—A supinator of the radial region, and antagonistic to the
pronators.
Flexor Metacarpi Radialis (Fig. 15, No. 10). Location.—The lowest of
the group of three muscles on the outer part of the forearm.
Origin.—By two tendinous heads, the longer from the external condyle
of the humerus, and the other just beyond the base of the olecranon.
Insertion.—Becomes tendinous at about the middle of the shaft of the
ulna and inserts to a prominent process on the proximal third of the

posterior part of the shaft of the mid-metacarpal.
Shape.—Fusiform.
Relations.—Inferiorly, the anconeus and superiorly, the extensor
digitorum communis.
Action.—A powerful flexor of the hand.
Pronator Brevis (Fig. 13, No. 18). Location.—Supero-lateral side of the
forearm.
Origin.—From just above the internal condyle of the humerus.
Insertion.—The tendon passing obliquely across the interosseous space
and is inserted to the ulnar side of the shaft of the radius, just beyond the
juncture of the proximal and the middle thirds.
Shape.—Fusiform.
Relations.—Superior to the pronator longus.
Action.—Pronates the forearm, and flexes the forearm upon the arm.
Pronator Longus (Fig. 14, No. 6). Location.—Lateral side of the radio-
ulnar region.
Origin.—From the middle of the internal condyle of the humerus.
Insertion.—To the shaft of the radius just beneath the pronator brevis.
Shape.—Massive, ellipsoidal.
Relations.—Between the pronator brevis and flexor digitorum profundus.
Action.—A pronator.
Extensor Ossis Metacarpi Pollicis (Fig. 13, No. 23). Location.—
Slightly interposed between the ulna and radius.
Origin.—Immediately in front of the greater sigmoid cavity of the ulna.
Insertion.—To the palmar side of the base of the first metacarpal, in
common with the extensor metacarpi radialis longior.
Shape.—Delicate, straight.
Relations.—Superiorly, the extensor indicis longus, and inferiorly, the
anconeus and the flexor digitorum profundus.
Action.—Extends the hand upon the forearm.
Anconeus (Fig. 15, No. 4). Location.—Between the ulna and the radius.

Origin.—By a short, strong, subcylindrical tendon from the lower
posterior of the external condyle of the humerus.
Insertion.—To the latero-radial side of the ulna somewhat beyond its
middle.
Shape.—Fusiform.
Relations.—Superiorly, the extensor indicis longus, and inferiorly, the
ulna.
Action.—A flexor of the forearm.
Extensor Indicis Longus (Fig. 13, No. 22; Fig. 15, No. 13). Location.—
Infero-lateral to the radius.
Origin.—From about one-half the surface of the proximal portion of the
radius.
Insertion.—Possesses a long tendon which passing over a groove at the
distal end of the ulna and receiving muscular fibers at the base of the
metacarpus, extends down the anterior part of the hand and is inclosed in a
sheath in front of the superior part of the first phalanx of the index-finger.
This tendon is inserted into the anterior upper rim of the distal phalanx.
Shape.—Small, thin.
Relations.—Supero-laterally with the radius.
Action.—Extensor of the digit.
Flexor Digitorum Sublimis. Location.—The forearm.
Origin.—From the internal condyle of the humerus.
Insertion.—Passing over the wrist, it is inserted to the middle phalanx of
the hand.
Shape.—A musculo-tendinous band, rather delicate and rudimentary.
Relations.—Closely adhering to the integument that stretches from the
internal condyle of the humerus to the wrist.
Action.—Assists these muscles. A flexor.
Flexor Digitorum Profundus (Fig. 13, No. 21). Location.—Lateral side
of the ulna.
Origin.—By two heads from the proximal extremity of the ulna, between
which the brachialis anticus passes.

Insertion.—The two bellies uniting are attached to the under side of the
shaft of the ulna. It becomes tendinous about the middle of the shaft, and
inserts to the ulnar side of the base of the distal joint of the index-finger.
Shape.—A fleshy belly with long tendon.
Relations.—Inferiorly, with the flexor carpi ulnaris, superiorly, with the
pronator brevis.
Action.—A flexor of the digit.
Flexor Carpi Ulnaris (Fig. 13, No. 19). Location.—Inferior part of the
forearm.
Origin.—By two strong tendons; one from the side and posterior of the
internal condyle of the humerus, passing through the humero-ulnar pulley at
the side of the base of the olecranon process; the other, to the posterior of
the internal condyle of the humerus. It does not pass through a pulley.
Insertion.—A subcylindrical tendon extends back of the ulnare ossicle of
the carpus giving off a tendinous slip to the flexor digitorum profundus, and
becomes inserted to the anterior rim of the proximal phalanx of the index
digit. It has an attachment at the carpus.
Shape.—A strong fleshy belly terminating in a long tendon.
Relations.—The outermost inferior muscle of the forearm.
Action.—A powerful flexor of the hand upon the forearm.
Flexor Carpi Ulnaris Brevior (Fig. 13, No. 20). Location.—Inferior
part of the antibrachial region.
Origin.—From a broad area on the middle third of the upper side of the
shaft of the ulna.
Insertion.—Near the top of the outer edge of the anchylosed os magnum
of the carpo-metacarpus.
Shape.—Thin, somewhat flat.
Relations.—To the inside of the flexor digitorum profundus.
Action.—Flexes the hand upon the forearm and rotates the hand toward
the body.

OTHER MUSCLES OF THE DIGITS

Extensor proprius pollicis
Flexor minimi digiti
Abductor minimi digiti
Interosseous palmaris
Flexor brevis pollicis
Flexor minimi digiti brevis
Interosseous dorsalis
Flexor metacarpi brevis

Extensor Proprius Pollicis (Fig. 13, No. 29a). Location.—Anterior to
the radio-carpal joint.
Origin.—From the ulnar side of the tendon of the extensor metacarpi
radialis longior.
Insertion.—To the antero-ulnar side of the pollex.
Shape.—Small, spindle-shaped; tendinous at both attachments.
Relations.—Inferiorly, with the proximal and anterior part of the
metacarpus.
Action.—An extensor of the pollex.
Flexor Brevis Pollicis (Fig. 13, No. 28a). Location.—Anterior to the
pollex.
Origin.—From the shaft of the mid-metacarpal bone, just below the
pollex.
Insertion.—Distal apex of the pollex.
Shape.—Short, small, fleshy.
Relations.—Superiorly, with the inferior part of the pollex.
Action.—Flexes the pollex.
Flexor Minimi Digiti. Location.—Inferior side of the metacarpus.
Origin.—From the posterior part of the median metacarpal close to the os
carpi ulnare. A few fibers extend to the ulna.
Insertion.—Into the base of the median phalanx.
Shape.—Small, slender, short.
Relations.—Superiorly, with the metacarpal bone.
Action.—A flexor of the digit.

Flexor Minimi Digiti Brevis (Fig. 13, No. 30). Location.—Inferior to
the third, or small finger.
Origin.—From the lower and posterior end of the median metacarpal and
from the adjacent tendon of the preceding.
Insertion.—Inserted to the apex of the small finger.
Shape.—Small and rather rudimentary.
Relations.—Inferior to the small finger.
Action.—Acts as a posterior ligament of this joint.
Abductor Minimi Digiti. Location.—Supero-lateral side of the small
finger.
Origin.—From the proximal extremity of the anterior aspect of the third
finger.
Insertion.—To the posterior border of the proximal phalanx of the
second, or index-finger at a point just above the tip of the third finger.
Shape.—A few muscular fibers with some tendinous material.
Relations.—At the base of the median segment of the index-finger and to
the side of the third.
Action.—Antagonizes the powerful flexors on the back of the joint.
Interosseus Dorsalis (Fig. 13, No. 31). Location.—By the side of the
metacarpus.
Origin.—From the margin of the shaft of the median metacarpal.
Insertion.—To the anterior part of the base of the distal phalanx of the
index digit.
Shape.—Short, delicate, with long tendon.
Relations.—Internally, the metacarpal bone.
Action.—Extends the last bone of the middle finger.
Interosseus Palmaris (Fig. 13, No. 32). Location.—On the opposite side
of the bone from the interosseous dorsalis.
Origin.—From the shaft of the median metacarpal under the preceding.
Insertion.—To the apex of the last joint of the second, or middle finger.
Shape.—Small, delicate, with long slender tendon.
Relations.—Beneath the preceding and along the metacarpal bone.

Action.—Flexes the terminal phalanx.
Flexor Metacarpi Brevis. Location.—To the lateral side of the
metacarpal bone.
Origin.—From the outer side of the distal extremity of the ulna.
Insertion.—To the base, in front, and on the ulnar side of the proximal
phalanx of the index digit.
Shape.—Delicate, with long slender tendon.
Relations.—On the lateral side of the ulna and the metacarpal bone.
Action.—Flexes the metacarpus.

MUSCLES OF THE POSTERIOR LIMB

Sartorius
Gluteus medius
Extensor femoris
Biceps flexor cruris
Semitendinosus accessorius
Femoro-caudal
Obturator internus
Abductor longus
Gluteus primus
Gluteus minimus
Vastus internus
Semitendinosus
Semimembranosus
Obturator externus
Gemellus
Adductor magnus

Sartorius (Fig. 23, No. 7). Location.—Extreme anterior portion of the
thigh.
Origin.—From the outer two-thirds of the superior surface of the raised
emarginations of the anterior border of the ilium, and by fascia from the
neural spines of the fourth dorsal vertebra.

Insertion.—Obliquely by a semitendinous fascia to the inner edge of the
ligamentum patella, and to the inner and adjacent border of the anterior half
of the summit of the tibia.
Shape.—Large, fleshy.
Relations.—Posteriorly, with the gluteus primus and the vasti.
Action.—Extends the leg, flexes and adducts the thigh.
Gluteus Primus (Fig. 23, No. 8 and 9). Location.—The outer flat
massive muscle of the thigh.
Origin.—By a thin fascia from nearly the entire length of the supero-
internal margin of the pre-acetabular portion of the ilium, above the
antitrochanter, and from the entire length of the post-acetabular ridge.
Insertion.—Near the patella it joins the tendon of the extensor femoris,
and by aponeurosis spreads over the knee and is inserted to the crest of the
upper border of the tibia, the patella being incorporated in its aponeurotic
ligament.
Shape.—Triangular in shape, it is aponeurotic anteriorly and more fleshy
posteriorly.
Relations.—Anteriorly, covers over the posterior portion of the sartorius
and the body of the gluteus medius; posteriorly, bordered by the
semitendinosus and the biceps.
Action.—Abducts the thigh.
Gluteus Medius (Fig. 24, No. 11). Location.—Supero-anterior part of
the ilium under the gluteus primus.
Origin.—From the entire supero-internal margin of the pre-acetabular
surface of the ilium and the concave surface on the adjacent bone.
Insertion.—By a strong tendon which passes over a bursa on the anterior
rim of the trochanter and is inserted obliquely to this trochanter.
Shape.—A fleshy muscle filling the concavity of the pre-acetabular
division of the ilium.
Relations.—Superiorly, with the gluteus primus; inferiorly, with the
gluteus minimus.
Action.—Abducts and pulls the femur forward.
Gluteus Minimus (Fig. 24, No. 12). (Synonym.—Gluteus profundus.)

Location.—Beneath the medius and the smaller of the two.
Origin.—To the anterior margin of the outer border of the ilium, and
from the supero-external surface of the last rib.
Insertion.—The fibers extending downward and backward and outward
become tendinous and are inserted below the trochanter of the outer part of
the upper third of the femur.
Shape.—Small, fleshy.
Relations.—Inferiorly, with the bone and superiorly, with the gluteus
medius.
Action.—Abducts and pulls the thigh forward.
Extensor Femoris (Fig. 24, No. 15). Location.—Anterior femoral
region. It is divided into two parts: the vastus externus and the crureus.
Origin.—The vastus extemus (Fig. 24, No. 14) arises tendinous from the
base of the trochanter of the outer part of the femur and from this point
down the bone approximately to the condyle. The crureus (Fig. 24, No. 13)
originates by a tendon from the anterior upper prominent rim of the
trochanter, from this point extending down the antero-external part of the
shaft of the femur.
Insertion.—Merges with the gluteus primus, and, by a fascia-like
arrangement, spreads over the front of the knee-joint inserts to the patella
and is also inserted into the crest of the tibia.
Shape.—Large, fleshy.
Relations.—Posteriorly, with the femur and anteriorly, with the sartorius.
Action.—Extends strongly the leg upon the thigh.
Vastus Internus (Fig. 16, No. 3). Location.—Internal and lateral side of
the femur.
Origin.—From the postero-internal part of the shaft of the femur just
below the head, and in a straight line extending down the femur.
Insertion.—By a broad tendon along the thickened inner border of the
summit of the tibia.
Shape.—Thick, long.
Relations.—Anteriorly, with the bone; surrounded by the other crural
muscles.

Action.—Extends the leg upon the knee; a powerful assistant of the
extensor femoris.
Biceps Flexor Cruris (Fig. 17, No. D, 1). Location.—Posterior tibial
region.
Origin.—By a tendinous fascia from the post-acetabular ridge, extending
between the antitrochanter and the anterior point of the insertion of the
semitendinosus.
Insertion.—To the tuberosity on the external part of the shaft of the fibula
a short distance below the head.
Shape.—Large, rather cone-shaped with base directed upward.
Relations.—Anteriorly, with the vastus externus; posteriorly, with the
semitendinosus. The inferior tendinous portion passes through a tendinous
sling or pulley called the biceps band.
Action.—Flexes the leg upon the thigh.
Semitendinosus (Fig. 23, No. 10). Location.—Posterior femoral region.
Origin.—By a tough, strong fascia from the surface of the caudal
muscles and from the posterior third of the post-acetabular ridge.
Insertion.—The fibers pass downward and forward, and insert to the
tendinous raphe along the posterior margin of the semitendinosus
accessorius; lower down it merges with the median fascia of the inner head
of the gastrocnemius.
Shape.—Fleshy, broad, flat and long.
Relations.—Internally, with the semimembranosus and anteriorly, with
the biceps flexor cruris.
Action.—Flexes the leg.
Semitendinosus Accessorius. Location.—Posterior femoral region.
Origin.—From an oblique line just above the condyle, on the posterior of
the shaft of the femur.
Insertion.—Its fibers, passing upward and backward, attach themselves
to the tendinous raphe common to this muscle and the semitendinosus, and
are finally inserted to the inner side of the shaft of the tibia.
Shape.—Flat, oblong.

Relations.—Posteriorly to the shaft of the femur, and externally to the
long adductors of the thigh.
Action.—Aids the preceding in flexing the leg.
Semimembranosus (Fig. 24, No. 17). Location.—Postero-internal to the
semitendinosus.
Origin.—From the outer surface of the ischium, beginning at the lower
margin of its notch on the posterior pelvic border, extends on a curved line
on the adjacent surface beyond.
Insertion.—The fibers, passing downward and forward, insert by a broad,
thin tendon to the shaft of the tibia a short distance below the head and on a
line parallel to the long axis of the tibia.
Shape.—Long, narrow, ribbon-shaped.
Relations.—Lies adjacent to the semitendinosus and in the same plane.
Action.—Directly flexes the leg.
Femoro-caudal (Fig. 24, No. 8). Location.—Infero-lateral to the caudal
and post-femoral region.
Origin.—By a delicate tendon from the base of the pygostyle.
Insertion.—By a thin, flat tendon upon the outer part of the shaft of the
femur below the trochanter and at about the juncture of the upper and
middle third of the bone.

Fig. 24.—Second layer of muscles of
the thigh of a cock. Outside view. 1,
Appendico-costales. 2, Levatores
costarum. 3, Sacro-lumbalis. 4,
Longissimus dorsi. 5, Intercostales. 6,
Longissimus dorsi. 7, Latissimus dorsi.
8, Femoro-caudal. 9, Edge of obturator
externus. 11, Gluteus medius. 12,
Gluteus minimus. 13, Crureus. 14,
Vastus externus. 15, Extensor femoris.
16, Biceps flexor cruris. 17,
Semimembranosus. 18, Adductor
magnus. 19, Adductor longus. 20,
External abdominal oblique. 21,
Depressor coccygis. 22, Tibialis anticus.
23, Tibialis posticus. 24, Flexor
perforans digitorum profundus. 25,
Flexor perforatus medius secundus
pedis. 26, Flexor longus hallucis.

Shape.—Long, narrow, spindle-shaped, flattened from side to side.
Relations.—Interiorly to the obturator externus, and along the upper
border of the long adductors of the thigh and the semimembranosus.
Action.—Pulls the tail down and to one side.
Obturator Externus (Fig. 24, No. 9). Location.—External posterolateral
side of the pelvis.
Origin.—From the posterior half of the periphery of the ischiatic foramen
and the concavity found on the external surface of the lateral part of the
pelvis.

Insertion.—The fibers pass across to the femur and are inserted by a
broad, flat tendon to the shaft of the femur just below the trochanter.
Shape.—Thick, fleshy.
Relations.—Lies just above the femoro-caudal muscle, the sciatic nerve
and femoral artery pass over and external to its tendon.
Action.—Pulls the head of the femur backward.
Obturator Internus (Fig. 16, No. E, 1). Location.—Occupies the space
between the ischium and the pubis.
Origin.—From the ventral surface of the ischium, including the posterior
border, from the inner line of the corresponding post-pubis, and from the
membrane covering the space between these two bones.
Insertion.—Becoming dense, subcylindrical, and strong, it passes
through the obturator foramen and is inserted to the outer part of the
trochanter of the femur, in common with the gemellus and opposite to the
insertion of the gluteus medius.
Shape.—Subtriangular and flat with a central tendon; bipenniform.
Relations.—Outside the pelvis the tendon lies upon the gemellus and is
external to it. Fills the obturator foramen and the space between the ischium
and the pubis.
Action.—Acts as a posterior stay to the head of the femur.
Gemellus (Fig. 25, No. 5). Location.—Posterior to the head of the femur.
Origin.—From the fossa between the acetabulum and the obturator
foramen, and on the outer side of the pelvis.
Insertion.—Its fibers are attached by fascia to the tendon of the obturator
internus, and pass directly to the trochanter of the femur where they insert
in common with that of the obturator internus.
Shape.—Strong, thick, chunky.
Relations.—Postero-external to the head of the femur.
Action.—Like the two preceding, when the head of the femur is fixed, it
pulls the pelvis forward and steadies it on the head of the femur.
Adductor Longus (Fig. 24, No. 19). Location.—In the posterior femoral
region.
Origin.—From a line on the lateral part of the pelvis.

Insertion.—The fibers, passing downward and forward, are inserted on a
longitudinal line along the posterior part of the shaft of the femur.
Shape.—Broad, flat, fleshy.
Relations.—Posteriorly to the femur, and anteriorly to the adductor
magnus.
Action.—Adducts the thigh.
Adductor Magnus (Fig. 24, No. 18). Location.—Posterior femoral
region.
Origin.—From the fine constituting the lower boundary of the ischiatic
fossa on the outer lateral part of the pelvis.
Insertion.—The fibers pass downward and are inserted to the superior
curve of the internal femoral condyle. The internal head of the
gastrocnemius blends with this muscle just above its attachment.
Shape.—Long, narrow.
Relations.—Posteriorly to the adductor magnus and anteriorly to the
semimembranosus.
Action.—Strongly adducts the thigh.

THE TIBIAL GROUP

Gastrocnemius
Peroneus longus
Extensor longus digitorum
Tibialis posticus
Flexor longus hallucis
Flexor perforatus annularis primus pedis
Flexor perforatus medius secundus pedis
Flexor perforans digitorum profundus
Soleus
Tibialis anticus
Extensor hallucis brevis
Flexor perforatus indicis secundus pedis
Flexor perforatus medius primus pedis
Flexor perforatus indicis primus pedis

Extensor brevis digitorum
Flexor hallucis brevis
Extensor annularis brevis
Gastrocnemius (Fig. 23, No. 11). Location.—Posterior tibial region.
Origin.—There are three heads: the internal, the external, and the tibial.
The external head extends by a short, flattened, strong tendon from the
postero-external part of the external condyle of the femur; the internal head
extends from the outer surface of the inner condyle of the femur; and the
tibial head extends from the entire inner rim of the tibial summit and from
the free edge of the adjacent crest.
Insertion.—At the lower fourth of the tibial shaft, terminates in a broad,
flat tendon which passes over the shallow, longitudinal groove of the tibial
cartilage, and, crossing the tibio-tarsal joint, is inserted to the posterior
surface of the hypotarsus of the metatarsal bone, and finally, below this
point, merges into the podothecal sheath confining the flexor tendons.
Shape.—Large, fleshy, somewhat cone-shaped with the base upward.
Relations.—The posterior fleshy muscle of the post-tibial region located
anterior to the soleus.
Action.—Extends the metatarsus on the tibia.
Soleus (Fig. 25, No. G, 1). Location.—The posterior tibial region.
Origin.—From the posterior part of the head of the tibia.
Insertion.—By a long slender tendon to the proximal end and toward the
inner angle of the tibial cartilage, some of the fibers passing to the tendon of
the gastrocnemius.
Shape.—Small, flattened.
Relations.—Anteriorly, with the flexor perforans digitorum profundus
and posteriorly, with the gastrocnemius.
Action.—Similar to that of the gastrocnemius.
Peroneus Longus (Fig. 23, No. 12). Location.—Antero-lateral tibial
region.
Origin.—From the raised crest in front of the head of the tibia, and from
the fascia that covers the outer side of the knee-joint.
Insertion.—The fibers, passing downward, then downward and outward,
terminate in a small tendon at the lower third of the tibia. This tendon

bifurcates just above the tibial condyles at the outer part of the limb, the
shorter and stronger attaches to the fibrous fascia covering the tibial
cartilage, the other merging with the tendon of the flexor perforatus medius
primus pedis about 1 centimeter below the hypotarsus of the tarso-
metatarsus.
Relations.—Covers over all the muscles of the anterior tibial region.
Shape.—A broad muscular sheet.
Action.—Assists the flexor perforatus medius primus pedis.
Tibialis Anticus (Fig. 24, No. 22). Location.—In the anterior tibial
region.
Origin.—The muscular belly may be easily divided into two parts. The
inner head extends from the head of the tibia immediately beneath the
peroneus longus. The outer head arises by a strong tendon from a
depression on the antero-inferior ridge of the outer condyle of the femur.
Insertion.—The tendon passing through the fibrous ligamentous loop just
above the tibial condyles, inserts to a tubercle on the shaft just below the
head of the tarso-metatarsus.
Shape.—Large, fusiform.
Relations.—Beneath the peroneus longus.
Action.—Flexes the metatarsus upon the tibia.
Extensor Longus Digitorum (Fig. 25, No. G, 6). Location.—Anterior
tibial region.
Origin.—From the inferior portion of the crest and a portion of the shaft
of the fibula.
Insertion.—It becomes tendinous at the lower third of the bone, passing
under the bony ridge just above the condyle in front, and over the ankle-
joint. It is bound down by firm fascia, and at the trochlea of the basal toe
joints, divides into three small tendinous slips. These pass over the superior
part of the second, the third, and the fourth toes, bifurcating in their course,
and are inserted to the distal ones.
Shape.—Long, penniform, with a long, slender tendon.
Relations.—Immediately below the tibialis anticus.
Action.—Extends the digits as their long extensor.

Extensor Hallucis Brevis (Fig. 25, No. G, 4). Location.—The anterior
metatarsal region, along the antero-internal edge.
Origin.—From just below the summit of the antero-internal part of the
head of the tarso-metatarsus, and from the adjacent shaft below, and from
the tendon of the tibialis anticus.
Insertion.—Into the process at the superior part of the bone of the bony
claw of the hallux.
Shape.—Slender, thin in diameter, with a long, slender tendon.
Relations.—Superiorly, with the antero-internal edge of the metatarsus
and interiorly, its tendon with the top of the hallux.
Action.—Extends the hallux.
Extensor Brevis Digitorum. Location.—On the anterior surface of the
metatarsus.

Fig. 25.—Inner layer of muscles of the
thigh of a hen. Outside view.

A. Pad of fibrocartilage or meniscus of
femoro-tibial articulation. 1, Inner semi-
lunar fibrocartilage. 2, External semi-
lunar cartilage. 3, Anterior border.

B. Tarsal meniscus or pad of
fibrocartilage.

C. Articular surface of the tarsal joint. 1,
Posterior ligamentum cruciatum genu.
2, Femoral tendinous insertion of tibialis
anticus. 3, Ligamentum tibio-fibulare. 4,
Ligamentum interosseum. 5,
Ligamentum transversum of the
meniscus. 6, Anterior ligamentum
cruciatum genu.

D. 1, Tibia. 2, Fibula. 3, Femur. 4,
External ligamentum laterale genu.

E. Inferior surface of the tail of a hen. 1,
Infracoccygis. 2, Lateralis coccygis.

F. Outside pelvic view. 1, Obturator
ligament. 2, Tendon of the obturator
internus. 3, Ligamentum oblongum. 4,
Ligamentum capsulare. 5, Gemellus.

G. Outside view of leg of a cock. 1,
Soleus. 2, Flexor longus hallucis. 3,
Flexor perforans digitorum profundus.
4, Extensor brevis hallucis. 5, Extensor
brevis annularis. 6, Extensor longus

digitorum. 7, Tendon of the tibialis
posticus.

H. 1, Transversalis abdominalis. 2,
Cotyloid cavity.

Origin.—By a small fleshy belly to the anterior part of the proximal end
of the metatarsus.
Insertion.—It becomes tendinous about the middle third of the
metatarsus. Extending down the anterior face of the metatarsus it is inserted
to the inner tubercle of the base of the first phalanx of the outer or fourth
toe.
Shape.—Long, slender.
Relations.—Posteriorly with the metatarsus.
Action.—Pulls the fourth toe upward and inward.
Flexor Hallucis Brevis. Location.—Postero-internal side of the
metatarsus.
Origin.—Side and lower margin of the inner aspect of the hypotarsus of
the tarso-metatarsus and from the shaft of this bone immediately below it.
Insertion.—Winds round inner side of basal joint of the hallux and is
inserted on its under side.
Shape.—Small flat muscle gradually tapering into a tendon.
Relations.—Posteriorly with the metatarsus.
Action.—To flex the hallux.
Extensor Annularis Brevis. Location.—On postero-external side of
metatarsus.
Origin.—External aspect of the hypotarsus and the shaft below.
Insertion.—Supero-external part of the basal phalanx of the fourth toe.
Shape.—Small flat muscle.
Relations.—Posteriorly with the metatarsus.
Action.—Extensor of the fourth toe.
Tibialis Posticus (Fig. 24, No. 23). Location.—In the posterior tibial
region.

Origin.—From the whole shaft of the fibula below the insertion of the
biceps flexor cruris, and from the shaft of the tibia a short distance below
this insertion. Also from the interosseous membrane, and the adjacent
surface of the tibial shaft.
Insertion.—Passing in front of the external malleolus, crossing the ankle-
joint, finally inserted into the outer edge of the summit of the tarso-
metatarsal bone.
Shape.—Long, subcylindrical.
Relations.—Medially, with the flexor perforans digitorum pedis;
superiorly, with the postero-external portion of the tibia.
Action.—Extends the metatarsus upon the tibia.
Flexor Perforatus Indicis Secundus Pedis (Fig. 17, No. 5). Location.—
The posterior tibial region.
Origin.—From the external surface of the outer condyle of the femur, just
below the head of the gastrocnemius.
Insertion.—Passing in an oblique manner along posterior to the tibia,
extends through the superficial part of the tibial cartilage to the outer side of
the leg; then crossing the tibio-tarsal joint, it passes through a special canal
of the hypotarsus, down the back of the tarso-metatarsus, under the annular
ligament of the sole of the foot and a cartilaginous structure below this
ligament, over the trochlea, and is inserted to the middle shaft of the second
phalanx of the second toe.
Shape.—Thin, flat, broadly spindle-shaped.
Relations.—Posteriorly, with the flexor perforatus medius secundus
pedis, and anteriorly, with the flexor perforatus annularis primus pedis.
Action.—Flexes the toes.
Flexor Longus Hallucis (Fig. 17, No. 7; Fig. 25, No. 2). Location.—The
posterior tibial region.
Origin.—By two tendinous heads: one from the posterior part of the
femur, just below the two condyles; the other from the outer part of the
external condyle of the femur. The deep flexor passes between these two
heads.
Insertion.—Becoming tendinous at the lower third of the leg, passes
beneath the superficial flexors in a special canal on the outer side of the

tibial cartilage, and extends through the large canal of the hypotarsus (Fig.
12, No. F, 5) next to the shaft, then down to the apex of the accessory
metacarpal bone. It is inserted to the tubercle on the inferior proximal end
of the ungual phalanx.
Shape.—Large, fusiform.
Relations.—With the exterior of the deep flexors.
Action.—Flexes the hallux as its long flexor.
Flexor Perforatus Annularis Primus Pedis (Fig. 17, Nos. D, 8 and C,
6). Location.—The posterior tibial region.
Origin.—From the inner side of the belly of the flexor longus hallucis.
Insertion.—Becoming tendinous at the lower third of the tibia, passes a
little to the outer side and through the tibial cartilage, then over the ankle-
joint and through the hypotarsal canal (Fig. 12, No. 5) to the under side of
the outer toe, where it forms a sheath through which the deep flexors
extend. It gives off on either side a tendinous slip which attaches to the
basal phalanx.
Shape.—Long, slender, compressed laterally.
Relations.—Internally, with the flexor perforatus indicis secundus pedis,
and externally, with the flexor longus hallucis.
Action.—Flexes the toes as their long flexor. A second flexor of the outer
toe.
Flexor Perforatus Medius Secundus Pedis (Fig. 17, No. 9). Location.
—The posterior tibial region.
Origin.—From a strong fascia that merges with the knee-joint, and by a
tendon from the external condyle of the femur in common with the tendon
of the flexor perforatus indicis secundus pedis.
Insertion.—Continued as a flattened tendon extending from the lower
third of the leg, passing obliquely through the tibial cartilage and then
through the interno-posterior canal of the hypotarsus, (Fig. 12, No. F, 5)
inserted to the second joint of the middle toe.
Shape.—Long, fusiform.
Relations.—With the shaft of the fibula, which it covers.
Action.—Flexes the middle toe.

Flexor Perforatus Medius Primus Pedis (Fig. 17, No. 2). Location.—
Posterior tibial region.
Origin.—From the inner side of the muscular portion of the flexor
perforatus annularis primus pedis.
Insertion.—Terminating in a flattened tendon, passes through the tibial
cartilage and hypotarsus, and then extends along the shaft of the basal joint
of the third toe, and, dividing into two slips, inserts to either side of its
shaft.
Shape.—Long, rather small.
Relations.—With the flexor perforatus annularis primus pedis on the
inner side.
Action.—Flexes the third toe.
Flexor Perforatus Indicis Primus Pedis (Fig. 17, No. 4). Location.—
The posterior tibial region.
Origin.—From a thin, broad tendon, on the external condyle of the
femur, in common with the flexor perforatus medius secundus pedis.
Insertion.—Becoming tendinous, passes through the tibial cartilage and
the hypotarsus of the metatarsus (Fig. 16, A) and inserts to the sides of the
basal joint of the second toe.
Shape.—Long, slender, fusiform; somewhat flattened laterally.
Relations.—With the flexor perforatus medius secundis pedis,
posteriorly.
Action.—A flexor of the toes.
Flexor Perforans Digitorum Profundus (Fig. 24, No. 24 and Fig. 25,
No. G, 3). Location.—The posterior tibial region.
Origin.—From the posterior part of the external condyle of the femur,
from the posterior part of the tibia just below the summit, and from a point
near the origin of the soleus.
Insertion.—Its heavy flattened tendon passes through the tibial cartilage,
this tendon dividing, the branches pass along the under side of the toes,
perforating the outer tendons and become inserted to the proximal tubercle
at the base of the under side of the ungual phalanxes of the second, third,
and fourth toes.
Shape.—Long, fleshy, with a long tendon.

Relations.—Closely with the tibial bone; the deepest of all the flexors.
Action.—Flexes the digits.

THE MUSCLES OF THE EYE

Orbicularis palpebrarum
Depressor palpebræ inferioris
Pyramidalis nictitans
Obliquus inferior
Rectus inferior
Levator palpebræ superioris
Quadratus nictitans
Obliquus superior
Rectus superior
Rectus externus
Rectus internus

Orbicularis Palpebrarum (Fig. 7, No. 30). (Synonym.—Orbicularis
oculi.)
Location.—Upon the lacrimal and maxillary bones.
Origin.—From the lacrimal and maxillary bones and the ciliary margin.
Insertion.—To the lower free edge of the tarsal cartilage.
Shape.—Thin, delicate layer of fibers.
Relations.—Externally, with the skin; internally, with the lacrimal and the
maxillary bones.
Action.—Aids in closing the eye.
Levator Palpebræ Superioris (Fig. 7, No. 24). Location.—Along the
superior roof of the orbit.
Origin.—Along a longitudinal line found near the middle of the roof of
the orbit.
Insertion.—To the ciliary margin of the upper lid, near the outer canthus.
Shape.—Thin, delicate layer.
Relations.—Superiorly, with the bony wall, and inferiorly, with the
eyeball.

Action.—Raises the superior eyelid.
Depressor Palpebræ Inferioris (Fig. 7, No. 29). (Synonym.—Malaris.)
Location.—Along the inferior border of the eye.
Origin.—From the inferior border of the interorbital foramen.
Insertion.—To the lower lid.
Shape.—Thin, flat, delicate.
Relations.—Superiorly, with the eyeball; inferiorly, with the inferior
orbital wall.
Action.—Pulls the lower lid down.
Quadratus Nictitans (Fig. 26, No. B, 7). Location.—Above the eyeball
along the inferior border of the upper wall of the orbit.
Origin.—From the sclerotic from the upper part of the ball.
Insertion.—To the upper part of the sheath of the optic nerve near the
optic foramen.
Shape.—Broad, thin, quadrate.
Relations.—Inferiorly, with the eyeball; superiorly, with the orbital wall,
with the superior oblique, and with the superior rectus.
Action.—Aids in pulling the nictitating membrane obliquely outward and
downward over the forepart of the eyeball.
Pyramidalis Nictitans (Fig. 26, No. B, 8). Location.—Inferoposteriorly
to the eyeball.
Origin.—From the lower nasal side of the eyeball.
Insertion.—The fibers converge toward the upper part of the optic nerve,
into a tendon which passes through a pulley at the free margin of the
quadratus. Inserts to the lower part of the margin of the third eyelid, the
nictitans.
Shape.—Pyramidal; of thin layers of fibers.
Relations.—Internally, with the bony orbital wall; externally, with the
eyeball.
Action.—Aids the quadratus nictitans.
Obliquus Superior (Fig. 26, No. B, 5). (Synonym.—Obliquus dorsalis.)
Location.—Superior to the eyeball.

Fig. 26.—Structures of the eye and
nasal passage.

A. 1, The anterior turbinated bone. 2,
The posterior turbinated bones. 3,
Orbital gland. 4, Ophthalmic division of
the fifth pair of cranial nerves. 5,
Section through the cerebrum. 6,
Section through the skull showing the
air spaces. 7, Section through the comb.
8, Anterior portion of the upper beak. 9,
Edge of the hard palate.

B. The intrinsic muscles of the eyeball.
1, Superior rectus. 2, Internal rectus. 3,
Inferior rectus. 4, External rectus. 5,
Superior oblique. 6, Inferior oblique. 7,
Quadratus. 8, Pyramidalis. 9, Optic
nerve. 10, Edge of membrana nictitans.

C. Posterior part of the eye showing at
the inferior portion of the ball the
pyramidalis muscle at 1, and at 2, the
quadratus. 3, Optic nerve.

D. Inner view of the posterior part of the
vitreous chamber. 1, Sclerotic coat. 2,
Choroid coat. 3, Retina. 4, Pecten.

E. Longitudinal section through the eye
of a hen. 1, Cornea. 2, Anterior
chamber. 3, Scleral ring. 4, Crystalline
lense. 5, Iris. 6, Retina. 7, Sclerotic. 8,
Choroid. 9, Pecten. 10, Optic nerve. 11,

Vitreous chamber.

F. An edge view of the crystalline lense
of a hen showing it to be asymmetrical
biconvex. 1, The anterior side. 2, The
posterior side.

G. The upper section through the
anterior portion of the anterior
turbinated bone showing one complete
circle and the lower a section through
the middle turbinated showing one and
one-half turns.

Origin.—From the orbital septum just back of the inner canthus, the
fibers passing backward and forward.
Insertion.—Into the sclera, anterior to the sclerotic plates.
Shape.—Small, thin, fan-shaped.
Relations.—With the eyeball, superiorly; at its extremities with the
superior rectus, interiorly.
Action.—Rotates the eyeball.
Obliquus Inferior (Fig. 26, No. B, 6). (Synonym.—Obliquus ventralis.)
Location.—Inferior to the eyeball.
Origin.—From the interorbital septum near the inner canthus of the eye.
Insertion.—By a broad expansion to the inferior portion of the eyeball.
Shape.—Tendinous at its insertions; fan-shaped as it passes downward
and outward.
Relations.—Internally, with the eyeball; and externally, with the bony
orbital wall, with the inferior rectus muscle, inferiorly.
Action.—Aids in rotating the eye; opposes the obliquus superior.
Rectus Superior (Fig. 26, No. B, 1). (Synonym.—Rectus dorsalis.)
Location.—Superior to the eyeball.
Origin.—Along the supero-posterior border of the optic foramen.
Insertion.—To the sclera just within the margin of the bony circle of the
eye.
Shape.—Flat, thin.

Relations.—Internally, with the obliquus superior; superiorly, with the
bony wall of the orbit.
Action.—To pull the eyeball upward.
Rectus Inferior (Fig. 26, No. B, 3). (Synonym.—Rectus ventralis.)
Location.—Inferior to the eyeball.
Origin.—From the inferior border of the optic foramen.
Insertion.—To the lower portion of the eyeball within the margin of the
bony circle of the eye.
Shape.—Thin, fan-shaped.
Relations.—Superiorly, with the eyeball; inferiorly, with the bony wall of
the orbit.
Action.—Pulls the eyeball downward.
Rectus Externus (Fig. 26, No. B, 4). (Synonym.—Rectus lateralis.)
Location.—External to the eyeball.
Origin.—By two heads infero-laterally to the optic foramen.
Insertion.—To the postero-external side of the eyeball.
Shape.—Short, fan-shaped.
Relations.—Internally, with the eyeball; externally, with the bony wall of
the orbit.
Action.—Pulls the eyeball outward.
Rectus Internus (Fig. 26, No. B, 2). (Synonym.—Rectus medialis.)
Location.—Inner side of the eyeball.
Origin.—From the supero-anterior border of the optic foramen.
Insertion.—To the sclera on the anterior portion of the eyeball.
Shape.—Thin, fan-shaped.
Relations.—Internally, with the eyeball and with the pyramidalis;
externally, with the bony wall of the orbit.
Action.—Pulls the eyeball inward.

THE MUSCLES OF THE EAR

Circumconcha
Tensor tympani

Circumconcha (Fig. 7, No. 32). Location.—Surrounds the external ear.
Origin and Insertion.—The circumconcha, surrounding the periphery of
the ear, is adherent to the skull and loosely to the skin, and is attached to the
outer terminus of the supra-occipital crest.
Relations.—Internally, with the skull; externally, with the skin.
Action.—Relaxes the tympanum.
Tensor Tympani (Fig. 7, No. 31). Location.—External to the quadrate
and to the external auditory meatus.
Origin and Insertion.—From the surface of the quadrate and the inner
end of the quadrato-jugal to the inner surface of the tympanum.
Shape.—A few fibers.
Relations.—Internally, with the quadrate and the quadrato-jugal;
externally, the integumental duplicature.
Action.—Tenses the tympanum.

FUNCTIONS OF MUSCLES

To cause the feathers on the top of the head to lie flat:
Dermo-frontalis.
To raise the feathers along the superior part of the neck and along the
dorsal region:
Dermo-dorsalis.
To tense the patagial region:
Dermo-tensor patagii,
Dermo-temporalis.
To cause the feathers to lie close to the body:
Dermo-humeralis,
Dermo-pectoralis.
To tense the lateral cervical integument:
Dermo-temporalis.
To support the lingual apparatus and superior larynx:
Platysma myoides.

To manipulate the feathers and skin of the inferior part of the neck:
Cleido-trachealis.
To control the skin in the shoulder region:
Dermo-spinalis.
To cause the feathers of the back to lie close to the skin:
Dermo-iliacus.
To depress the humeral region:
Dermo-ulnaris.
To close the jaw:
Temporalis,
Pterygoideus internus,
Pterygoideus externus,
Masseter.
To open the jaw:
Biventer maxilla,
Entotympanic.
To raise the trachea and hyoid apparatus:
Digastricus.
To elevate the tongue:
Mylo-hyoideus.
To pull the tongue to one side:
Singly[5]—
Cerato-hyoideus,
Stylo-hyoideus.
Alone when the larynx is fixed—
Sterno-hyoideus.
Those which protrude the tongue from the mouth:
Together—
Cerato-hyoideus,
Genio-hyoideus.
To aid in deglutition:
When the base of the tongue is fixed—
Sterno-hyoideus.
To depress the tongue:
Together—
Sterno-hyoideus.
To depress the tip of the tongue and elevate the base:

Depressor glottis.
To elevate the hyoid arches:
Cerato-glossus.
To extend the head:
Complexus,
Rectus capitis anticus minor.
To flex the head upon the neck:
Flexor capitis inferior.
To extend the head on the neck and elevate the neck:
Biventer cervicis.
To raise the neck upward:
Longus colli posticus.
To flex each vertebra on the preceding or succeeding laterally:
Obliquus colli,
Intertransversales.
To pull the neck downward:
Longus colli anterior.
To pull the head downward:
Together—
Rectus capitis lateralis,
Trachelo-mastoideus.
To pull the head downward and to one side:
Singly—
Rectus capitis lateralis,
Trachelo-mastoideus.
To approximate the spinous processes of the vertebræ:
Interspinales.
To approximate the vertebræ in a supero-lateral direction:
Interarticulares.
To flex the vertebræ supero-laterally:
Obliquo-transversales.
To extend the neck:
Together when the first rib is fixed—
Scalenus medius.
To close the glottis:
Constrictor glottidis.
To open the glottis:

Thyreo-arytenoideus.
To approximate the tracheal rings:
Tracheo-lateralis.
To tense the inferior larynx:
Broncho-trachealis posticus,
Broncho-trachealis anticus,
Broncho-trachealis brevis,
Bronchialis posticus,
Bronchialis anticus.
To relax the inferior larynx:
Sterno-trachealis.
To aid in respiration:
When the first rib is fixed—
Intercostales.
When wing is fixed—
Latissimus dorsi,
Dermo-cleido dorsalis.
When the scapula is fixed—
Serratus magnus anticus,
Serratus parvus anticus,
Thoraco-scapularis,
Levatores costarum,
Appendico-costales,
Triangularis sterni.
To flex the shoulder-joint:
Latissimus dorsi.
To elevate the humerus:
Latissimus dorsi.
To draw the scapula forward:
Trapezius,
Rhomboideus.
To close the wing:
Teres et infraspinatus.
To extend the humerus:
Coraco-humeralis,
Scapulo-humeralis.
To pull the humerus upward and backward:

When the scapula is fixed—
Supraspinatus.
To pull the coracoid outward:
Subclavius.
To depress the wing:
Coraco-brachialis.
To depress the scapula:
When the ribs are fixed—
Thoraco-scapularis.
To rotate the humerus:
Subscapularis.
To flex the forearm:
Pronator brevis,
Biceps,
Brachialis anticus,
Anconeus,
Tensor patagii longus,
Tensor patagii brevis.
To extend the arm:
Deltoid.
To extend the antibrachial region:
Triceps.
To raise and to draw the hand forward:
Extensor metacarpi radialis longior.
To extend the digit:
Extensor indicis longus,
Extensor digitorum communis,
Extensor proprius pollicis,
Interosseous dorsalis.
To supinate the radial region:
Supinator brevis.
To flex the hand:
Flexor metacarpi radialis.
To pronate the forearm:
Pronator brevis,
Pronator longus.
To extend the hand on the forearm:

Extensor ossis metacarpi pollicis.
To flex the digit:
Flexor minimi digiti,
Flexor digitorum sublimis,
Flexor brevis pollicis,
Flexor digitorum profundus,
Interosseous palmaris.
To flex the hand upon the forearm:
Flexor carpi ulnaris,
Flexor carpi ulnaris brevior.
To rotate the hand toward the body:
Flexor carpi ulnaris brevior.
To abduct the digits:
Abductor minimi digiti.
To flex the metacarpus:
Flexor metacarpi brevis.
To extend the leg:
Sartorius.
To adduct the thigh:
Sartorius,
Adductor longus,
Adductor magnus.
To abduct the thigh:
Gluteus primus,
Gluteus medius,
Gluteus minimus.
To pull the thigh forward:
Gluteus minimus,
Gluteus medius.
To extend the leg upon the thigh:
Extensor femoris,
Vastus internus.
To extend the leg upon the knee:
Vastus internus.
To flex the leg upon the thigh:
Biceps flexor cruris,
Semitendinosus,

Semitendinosus accessorius,
Semimembranosus.
To pull the tail down and to one side:
Femoro-caudal.
To pull the head of the femur backward:
Obturator externus.
To act as a posterior stay to the head of the femur:
Obturator internus.
To pull the pelvis forward and to steady it on the head of the femur:
Gemellus,
Obturator internus,
Obturator externus.
To extend the metatarsus on the tibia:
Gastrocnemius,
Soleus,
Tibialis posticus.
To flex the toes:
Peroneus longus,
Flexor perforatus medius primus pedis,
Flexor perforatus indicis secundus pedis,
Flexor perforatus medius secundus pedis,
Flexor perforatus indicis primus pedis,
Flexor perforans digitorum profundus,
Flexor longus hallucis,
Flexor perforatus annularis primus pedis.
To flex the metatarsus on the tibia:
Tibialis anticus.
To extend the toes:
Extensor longus digitorum,
Extensor hallucis brevis.
To flex the back laterally and to aid in raising the body.
Sacro-lumbalis,
Longissimus dorsi.
To elevate the tail:
Levator coccygis,
Levator caudæ.
To depress the tail:

Depressor caudæ,
Infracoccygis.
Together—
Depressor coccygis,
Lateralis caudæ.
To pull the tail downward and to one side:
Singly—
Lateralis coccygis.
Depressor coccygis,
Lateralis caudæ.
To close the eyelids:
Orbicularis palpebrarum.
To raise the superior eyelid:
Levator palpebræ superioris.
To pull the lower eyelid downward:
Depressor palpebræ inferioris.
To pull the membrana nictitans over the eyeball:
Quadratus nictitans,
Pyramidalis nictitans.
To rotate the eyeball:
Obliquus superior,
Obliquus inferior.
To pull the eyeball upward:
Rectus superior.
To pull the eyeball downward:
Rectus inferior.
To pull the eyeball outward:
Rectus externus.
To pull the eyeball inward:
Rectus internus.
To tense the ear drum:
Tensor tympani.
To relax the ear drum:
Circumconcha.
To depress the humerus:
Pectoralis major.
To raise the humerus:

Pectoralis secundus,
Pectoralis tertius.
5. Muscles are arranged in pairs. Singly means one muscle acting alone, i.e., without its fellow;
together means acting both at the same time.

SPLANCHNOLOGY

The Digestive Apparatus.—This apparatus, apparatus digestorius,
consists of the organs directly concerned in the reception of food, in its
passage through the body, and in the expulsion of the unabsorbed portion.
For convenience, these organs are grouped as follows: the alimentary canal
and the accessory organs.
The alimentary canal is a tube which extends from the mouth to the anus.
It has a complete lining of mucous membrane, external to which is an
almost continuous muscular coat. The abdominal portion of the tube is
largely covered with a serous membrane, the visceral peritoneum. The canal
consists of the following consecutive segments: mouth, pharynx, first
portion of the esophagus, crop, second portion of the esophagus,
proventriculus, gizzard, small intestine, large intestine, and cloaca.
The accessory organs are beak, tongue, salivary glands, liver, and
pancreas.
The Mouth (Fig. 27).—The distinctive character of the mouth of the
fowl consists, in the absence of lips and teeth and instead of jaw bones of
other animals, of a beak. The edge of the beak is covered by a horn-like
gum. The shape of the beak differs in the various classes of birds. In the
chicken the beak is short, strong, thick, and pointed; in palmipeds it is
flattened. The upper mandible extends out over the lower mandible. The
outer portion of the upper and the lower beaks is covered by a horny sheath.
There is no velum, and the mouth cavity is extended rather continuously
into the pharynx (Fig. 27, No. 4). The posterior cross bar of the hard palate
(Fig. 27, No. 5), which possesses a row of filiform papillæ projecting
backward, marks the upper boundary line of the mouth; while the posterior
end of the tongue (Fig. 27, No. 6), likewise with a row of filiform papillæ,
marks its lower boundary line.

Parts of the Mouth.—The mouth of fowls is divided into an upper and a
lower half. The upper half is divided into an anterior and a posterior part.
The anterior part extends from the anterior tip of the beak to the posterior
nares. It is further divided into an outer hard part and an inner soft part. The
outer part is covered by epithelium which may be considered as a
continuation from the upper outer portion of the beak. A portion of this is
cornified. The inner part is covered by a mucous membrane containing
mucous glands, nerves, and blood-vessels.
In the posterior part of the upper half of the mouth, are situated the
posterior nares (Fig. 27, No. 10) which appear as a longitudinal slit in the
center of the hard palate. There is also found in this part a furrow which
contains the opening of the Eustachian tubes, or tubæ auditivæ. There are
also two ridges near the same posterior part in which are red and white
papillæ, which may appear in rows, and which contain mucous glands.

Fig. 27.—Mouth and pharynx of a cock
laid open. 1, Eye. 2, Edge of beak
covered with a horn-like gum. 3,
Tongue. 4, Pharynx. 5, Posterior cross
bar of hard palate. 6, Posterior end of
tongue. 7, Anterior end of esophagus. 8,
Phrenum. 9, Palatal papillaries. 10,
Posterior nares.

The lower half of the mouth lies between the lower jaw bones and the
walls of the mouth cavity. The tongue is attached here by means of the
phrenum (Fig. 27, No. 8). This half of the mouth forms a pocket-like
structure which aids in taking up the food.

The mouth cavity is lined with stratified squamous epithelium,
continuous with that of the pharynx and the esophagus. Taste buds are
located in the mucous membrane of the mouth.

Fig. 28.—Various anatomical parts of the fowl.

C. A section through the nasal region of the fowl. 1, Nasal passages showing the
turbinated bones dividing the nasal passage into the superior, middle and inferior
meati. 2, The infraorbital sinus. 3, The hard palate.

D. Herbst’s touch corpuscle from the beak of a quail.

E. A vertical section through the ductus cochlearis of a pigeon. 1, A blood-vessel.
2, The periosteum. 3, The bony structure. 4, The vascular integument. 5. The
scala vestibuli. 6, The inner hyaline cylindrical cells. 7, The membrana tectoria.
8, The papilla acustica basilaris. 9, The membrana basilaris. 10, The scala
tympani. 11, The ganglion of the cochlear nerve in the ramus basilaris. 12, The
periosteum (Gadow).

F. A corpuscle of the soft papilla of a duck’s tongue.

J. A transverse section through a feather papilla. 1, The pulp. 2, The malpighian
layer. 3, The corium. 4, The stratum corneum of the papilla. 5, The malpighian
cell group of the main shaft. 6, The horny sheath.

In many water fowls, as geese and ducks, the gum edge of the mandible
has grooves extending crosswise, in which are numerous terminals of the
trigeminus nerve arranged as taste organs (Fig. 29, G and Fig. 28, D and F).
In many birds of prey and in water birds, e.g., the goose and the duck, there
is found at the base of the beak, a very thin, nervous or sensitive skin, waxy
in appearance, called the ceroma.

Fig. 29.—Various anatomical parts of
the fowl.

A. 1, The superior semicircular canal. 2,
The vestibular nerve. 3, The meatus
auditorius internus—the entrance of the
auditory nerve. 4, The entrance of the
cochlear nerve. 5, Posterior semicircular
canal. 6, The ampulla.

B. Side papilla of the tongue. 1 and 2,
Papillæ showing a fibrous central core
supporting blood-vessels and nerves. 3,
The basement membrane consisting of
connective tissue.

G. Herbst’s corpuscle of the tongue of a
duck, showing the capsule, lamella and
around the nerve zone, numerous round
bodies arranged in two rows.

H. From the cristæ acoustica of the
ampulla of the dove. A, A vertical

section with isolated fiber cells. 1 and 2,
The nerve fibers. 3, The hair cells.

I. A longitudinal section through a
feather papilla showing a young feather.
1, The developing feather. 2, The horny
sheath. 3, The epithelium. 4, Stratum
corneum. 5, Stratum malpighi. 6,
Corium. 7, Malpighian cell group of the
follicle.

The Hard Palate.—The hard palate, palatum durum, forming the roof of
the mouth has for its boundaries the beak anteriorly, the mandibular arches
laterally, and the pharynx posteriorly. It has four or five transverse bars,
projecting posteriorly from each of which is a row of filiform papillæ (Figs.
27 and 29).

Fig. 30.—A section through the wall of
the crop of a hen. 1, The outer muscular
layer showing longitudinal fibers. 2, The
inner muscular layer showing the
sectioned ends of the bundles of muscle
fibers. 3, Stratified squamous
epithelium. 4, The outer surface or
lumen of a fold. 5, The stroma,
muscularis mucosa, and submucosa.

The beak (Fig. 4, No. 1) with little if any aid from the tongue, is the
prehensile organ.

The Tongue (Fig. 27, No. 3). Location.—The tongue (lingua) of the fowl
is situated in the floor of the mouth between the rami of the lower mandible,
and is slung to the cranium by the cerato-branchial element of the os
hyoideum (Fig. 18, No. 2).
Shape.—The tongue, is pointed in front and wide behind, shaped like an
Indian arrow-head, and is supported by the bony and cartilaginous hyoid
apparatus (Fig. 9, A).

Fig. 31.—The visceral organs of the
hen. 1, Tongue. 2, Larynx. 3, Glottis. 4,
First portion of the esophagus. 5, Crop.
6, Second portion of the esophagus. 7,
Proventriculus. 8, Duodenum. 9, Free or
floating portion of the small intestine.
10, Mesentery supporting the free
portion of the small intestine. 11, Cæca.
12, Rectum or large intestine. 13,
Cloaca. 14, Anus. 15, Liver. 16, Gall-
bladder. 17, Pancreas. 18, Gizzard. 19,
Trachea. 20, Lungs. 21, Spleen.

Structure.—The free part of the tongue consists of two long tubes which
are formed by the rolling in of the ventral sides of its horny coverings. The
dorsal plate, which constitutes one-half of the horny sheath, does not form
a part of the tubes, but ends in the region of the point of the entoglossum.

The top surface is covered by a thick stratum corneum, giving it a rather
horny surface. Glands occur in the posterior part of the tongue.
While not so freely movable as in mammals, the tongues of birds are
very flexible.
The Pharynx (Fig. 27). Location.—The anterior part of the pharynx
joins with the mouth and the posterior part with the upper portion of the
esophagus and the superior larynx. The pharynx is bounded anteriorly by
the base of the tongue and by the posterior edge of the hard palate.
Posteriorly, it is marked by the entrance of the esophagus and by a ridge of
filiform papillæ located on the supero-posterior part of the larynx, called the
palatal papillaries. A few filiform papillæ stud the roof. The pharynx
communicates anteriorly with the posterior nares and the mouth, and,
posteriorly, with the esophagus and the larynx.
Shape.—The pharynx is a musculo-membranous sac.
Structure.—The pharynx is lined with a mucous membrane covered by
squamous epithelium. The mucous membrane is thrown into irregular folds.
The bird has two Eustachian tubes. Pneumatic apertures conduct the air
from the Eustachian tubes to the pericranial diploë.
In the posterior pharyngeal roof is situated the infundibular crevice.
Function.—The function of the pharynx is to give passage for the air
from the posterior nares to the larynx, and to give passage for the food from
the mouth to the esophagus.
Glands Adjacent to the Mouth and to the Pharynx.—The mucous
membrane adjacent to the glottis and in the roof of the mouth contains
alveolar glands. The angular gland of the mouth, located beneath the
zygomatic arch, by some anatomists is considered the rudimentary parotid
gland. The sublingual glands, or glandulæ sublinguales, are well developed
(Fig. 17, No. B, 4). They form conical masses, with the apex directed
anteriorly, and occupy a portion of the intermaxillary space. Several ducts
from these glands open into the mouth cavity. In the palatine region there
are also located glands called the palatine glands, which open by many
stomata upon the surface.
The Esophagus (Fig. 18, No. 6). Location and Shape.—The esophagus
is a musculo-membranous tube, capable of great distension, which extends
from the pharynx to the proventriculus (Fig. 35, No. 1, and 3).

The esophagus communicates anteriorly with the pharynx. It extends
down the neck, lying supero-laterally with regard to the trachea and toward
the right side. It enters the thorax above the trachea, and, passing through
between the bronchi, terminates into the proventriculus. At the entrance of
the thorax and just to the right of the median line, it expands into the crop
which divides it into two portions, designated as the first and the second.
The first portion of the esophagus is the longer, the length depending upon
the size and kind of fowl.
Structure.—The wall is composed of four coats, the mucous membrane,
the submucosa, the muscular coats, and the fibrous sheath or tunic. The
mucous membrane is pale and is covered with stratified squamous
epithelium.
The mucous membrane is loosely attached to the muscular coat by the
submucosa. Except during deglutition it lies in longitudinal folds which
obliterate the lumen. Opening from the mucosa are lenticular glands, which
may be seen on inflating an esophagus and looking through its transparent
walls.
The muscular coat of the esophagus is divided into two layers, an outer
longitudinal and an inner circular layer.
The outer fibrous sheath connects the esophagus loosely to the
surrounding structures.
Function.—The function of the esophagus is to give passage way for the
food from the pharynx to the crop and from the crop to the proventriculus.
The Crop (Fig. 35, No. 2; Figs. 30 and 31). Location and Shape.—The
crop, or ingluvies, saccular in shape, is located at the entrance of the thorax
and just to the right of the median line. The first portion of the esophagus
empties into the crop superiorly and inferiorly the crop opens into the
second portion of the esophagus. Like the esophagus the crop is capable of
great distension.
Structure.—The wall of the crop is composed of four coats, the mucous
membrane, submucosa, muscular and the outer fibrous.
The crop is lined with mucous membrane containing mucous glands
which secrete a mucus to keep the surface moist. The surface of the mucous
membrane is covered by stratified squamous epithelium.
The submucosa connects the mucous membrane to the muscular coat.

The wall of the crop is provided with strong muscles. The fibrous coat, or
tunic, connects it with the surrounding structures.
Function.—The crop is a storehouse for the food during the hours of
feeding, the food when needed by the stomach being gradually discharged
from the crop by the contraction of its muscular walls. The subcutaneous
cervical muscles which cover this reservoir aid in this discharge.
In the act of deglutition, the food, after being subjected to the fluid
supplied in the mouth by the adjacent glands, is poised upon the tongue and
swallowed partly by a sudden jerk of the head, and partly by means of the
pressure of the tongue against the hard palate, the food then passes down
the esophagus and lodges first in the crop, till needed by the stomach, when
it is passed through the second portion of the esophagus to the first portion
of the stomach, the proventriculus. The time during which food remains in
the crop depends upon the nature of the food. Animal food will, in part, be
retained about eight hours and vegetable foods may not all be passed on for
from sixteen to eighteen hours.
The Stomach (Fig. 31, No. 7; Fig. 32, B).—The stomach, or ventriculus,
of fowls is made up of two portions, namely, the pars glandularis, or
proventriculus, and the pars muscularis, or gizzard.
The Proventriculus. Location.—The proventriculus lies in the superior
part of the groove formed by the two lobes of the liver, is inferior to the
aorta, and is directed slightly to the left, communicating anteriorly with the
second portion of the esophagus and posteriorly emptying into the pars
muscularis, the gizzard.
Shape.—The proventriculus is round transversely and elongated, in fact,
nearly fusiform. In the hen of average size it measures about 1.62 inches
long and 0.8 inch in diameter.
Structure.—The wall of the proventriculus has four coats, the mucous,
submucous, muscular, and serous.
The inner mucous coat which is raised in folds, is lined with columnar
epithelial cells. The mucous membrane contains lymphoid tissue. The
mucous coat throughout contains simple tubular glands which secrete a
highly acid fluid which finds its way to the surface through small
cylindrical ducts lying at right angles to the inner surface of the mucous
membrane (Fig. 32, No. B, 1).

Fig. 32.—Gizzard and stomach of the
fowl.

A. 1, Alveolar glands. 2, Mucous
membrane of the inner surface of the
proventriculus showing the tubular
glands. 3, Connective tissue between the
alveolar glands. 4, An artery. 5,
Muscularis mucosa.

B. Photograph of the proventriculus and
gizzard. 1, Proventriculus showing
stomata of glands. 2, End of duodenum.
3, Gizzard showing hornified epithelium
formed into grooves. 4, The heavy
muscular walls.

The submucosa, connects the mucous and muscular coats and the
muscularis layer throws the mucous membrane into folds.
Outside the muscularis mucosa there is another layer (Fig. 32, A), of
simple tubular glands, grouped in lobules, and lined by cuboidal cells and

separated from each other by clefts. These tubular glands converge toward
the center and open into the same cavity.
The middle muscular coat can be divided into three layers: two thin,
longitudinal layers, and a thick, circular layer interposed between the other
two.
Function.—The function of the proventriculus appears to be to soak the
food with a secretion. The secretion from the proventriculus is similar to
that produced by the fundus glands of the stomach of mammals. It contains
acid and a ferment-pepsin.
The Gizzard (Fig. 31, No. 18). Location.—The gizzard, or muscular
stomach, occupies a portion of the central part of the abdominal cavity (Fig.
33, No. 4). It lies slightly to the left and just behind the liver, the
proventriculus, and the spleen, and rests upon a mass of intestines. The
gizzard communicates at its anterior portion with the proventriculus and
with the duodenum. These openings are close together. The gizzards of a
large number of hens of average size averaged in weight as follows: full,
0.215 pound; empty, 0.126 pound. The gizzard stands perpendicularly and
somewhat obliquely in the abdominal cavity.
Shape.—In shape the gizzard is roundish, flattened laterally.
Structure.—The walls of the gizzard are very thick and are made up of
three coats: mucous, muscular, and serous.
The cavity of the gizzard is covered by a thick skin-like structure
possessing a heavy stratified squamous epithelial layer which is thrown
somewhat into ridges (Fig. 32, B). This membrane becomes thinnest near
the edges.
The mucous membrane, being cornified and readily detachable, is by
some anatomists considered as a special membrane (Fig. 37, B).
At the pyloric opening there is a valve formed by a fold of the mucous
membrane, which prevents grit and large particles of food from passing out
of the gizzard.

Fig. 33.—View of viscera of the left side of a hen. 1, The base of the heart. 2,
Proventriculus. 3, Left lobe of the liver. 4, Gizzard. 5, End of the duodenal loop.
6, Pancreas. 7, Free portion of the small intestine. 8, Lungs. 9, Diaphragm.

Fig. 34.—View of the viscera of the right side of a hen. 1, Base of the heart. 2,
Lungs. 3, Right lobe of the liver. 4, Duodenal loop. 5, Pancreas. 6, Cæcum. 7,
Large intestine or rectum. 8, Free portion of the floating small intestine. 9, Gall-
bladder. 10, Right kidney. 11, The ribs. Note the lungs pushing up between them.

On each side it has a powerful fleshy muscle, the muscularis lateralis.
These musculares laterales are hemispherical, consist of very closely
packed fibers extending transversely, and are attached to strong anterior and
posterior ligamentous tendons. They are joined at the edge of the organ by a

strong aponeurosis. The muscular fibers are red but do not possess cross
striations; they are of the smooth type. The muscularis intermedii, thinner
and less developed than the musculares laterales, occurs on each of the
anterior and the posterior parts of the gizzard.
The serous coat covers over the greater part of the external surface of the
gizzard and closely adheres to the muscular coat.
Function.—The hard callous pads of the gizzard, operated by the
powerful muscles above described, together with grit, act like mill stones
and make reduction to fineness very complete.
At the posterior part there is a sacculated portion containing glands of the
long tubular type which secrete a fluid ferment similar to that secreted by
the glands of the pyloric portion of the stomach of mammals. These glands
also exist in a small band near the entrance of the gizzard. Here the food is
mixed with strongly acid secretion containing pepsin which makes gastric
digestion perfect.

Fig. 35.—A median antero-posterior section through the body of a 1-pound
pullet. 1, First portion of the esophagus. 2, Crop. 3, Second portion of the
intestine. 4, Proventriculus. 5, Gizzard. 6, Spleen. 7, Liver. 8, Heart. 9, Point
where duodenum was severed from gizzard. 10, Point where duodenum was
severed. 11, Duodenum. 12, Pancreas. 13, Cæcum. 14, Floating small intestine.
15, Ovary. 16, Oil sac.

The Small Intestine (Fig. 31, No. 8 and 9).—The small intestine,
intestinum tenue, is the tube which connects the gizzard with the large
intestine. It is divided into two parts, the duodenum and the free portion. Of
the three parts as considered in the mammalian intestine, only the first, the
duodenum, can be distinguished. There is no demarcation between the
jejunum and the ileum. The jejunum and the ileum or that part which
represents these sections, are in coils suspended from the free border of the
mesentery the other border of which is, in turn, attached to the dorsal wall
(Fig. 64). The length of the small intestine in a hen of average size is about
61.7 inches.

Fig. 36.

A. Section of the duodenum of the fowl.
1, Villus. 2, Gland. 3, Mass of lymphoid
tissue. 4, Muscularis mucosa. 5,
Longitudinal layer. 6, Circular muscular
layer. 7, Serous layer.

B. A section from A at a. 1, The striated
free border of the cells. 2, Goblet cell. 3,
Columnar cell. 4, Nucleus of cell.

The wall of the small intestine is provided with four coats, as follows: a
mucous, submucous, muscular coat made up of two layers—the outer,
longitudinal and the inner circular layer, and an external serous.

Fig. 37.—Histological studies of various anatomical parts.

A. A transverse section of the first portion of the esophagus of a fowl. 1, The
outer longitudinal muscular layer. 2, The circular muscular layer. 3, The
submucosa. 4, The muscularis mucosa. 5, Stroma. 6, Epithelial layer. 7, The
lenticular glands. 8, The lumen.

B. A transverse section of the proventriculus. 1, The outer longitudinal muscular
layer. 2, The middle muscular layer. 3, The inner longitudinal muscular layer. 4,
Stroma. 5, The muscularis mucosa. 6, The submucosa. 7, Stroma. 8, Tubular
glands. 9, Tubulo-alveolar glands. 10, A tubulo-alveolar gland with the tubular
glands cut transversely, 11, The lumen of the proventriculus.

C. A section of the inner wall of the gizzard. 1, The hyaline mucous membrane.
2, Branched tubular glands. 3, Submucosa. 4, Muscle. 5, A connective tissue
septum.

D. A transverse section of the small intestines. 1, The outer longitudinal muscular
layer. 2, The inner circular muscular layer. 3, The muscularis mucosa. 4, The
stroma. 5, Brunner’s glands. 6, A villus. 7, Mass of lymphoid tissue.

E. A transverse section through the cecum. 1, The outer longitudinal muscular
layer. 2, The inner circular muscular layer. 3, The submucosa. 4, The muscularis
mucosa. 5, The stroma. 6, Tubular glands. 7, The lumen.

F. The cerebellum showing the arbo-vitæ. 1, White, fiber portion. 2, The granular
layer. 3, The layer of Purkinje cells. 4, The molecular layer.

The mucous membrane which lines the intestine is thick, soft, and highly
vascular. It has a velvety appearance, due to numerous long, thin projecting
villi. The villi (Fig. 36, A) are concerned in the absorption of the digested
food, absorbing principally the emulsified fats. Each villus is covered with a
single layer of high columnar epithelial cells. Some of these, the so-called
goblet cells, provide mucin which lubricates the mucous surface. These
cells are found in all mucous surfaces and prevent the surface from
becoming dry. There are a few goblet cells near the summits of the villi.
Openings of simple intestinal tubular glands the duodenal glands, or the
glands formerly known as Brunner’s glands, are located between the villi.
These glands secrete the succus entericus, or intestinal juice. These
openings, or stomata, are lined with granular cells. The reaction of the
contents of the small intestine is strongly acid, but gradually less so in
proportion to the distance down the intestinal tract until the cæca are
reached, where the reaction is found to be faintly acid, neutral, or slightly
alkaline.
Function.—The function of the small intestine is that of digestion and
absorption.
The Duodenum. Location and Shape.—The duodenum, a small tube,
originates from the gizzard about ½ inch to the right of the entrance of the
proventriculus. Extending from left to right, it passes under and behind the
gizzard along the inner side of the right abdominal wall backward to the
posterior portion of the wall, and a trifle more than half way toward the left
side, where the loop rests. This loop, the duodenal loop, is about 5 inches in
length (Fig. 31, No. 8). The two branches of the loop the first and the
second portions or the descending and ascending limbs, are loosely held by
connective tissue, and have the pancreas lodged between them.
The Free Portion of the Small Intestine. Location.—That section of the
small intestine following the duodenum is called the free portion of the
small intestine and occupies the space between the abdominal air-sac and
the median line of the abdominal cavity. It is disposed in coils and is
suspended from the dorsal wall of the abdomen by a thin membrane, the
mesentery.
The bile ducts enter the small intestine about 14 inches from its point of
origin. The pancreas also pours its contents into the small intestine.

The Large Intestine (Fig. 31, No. 12). Location.—The large intestine
extends in a straight line along the inferior border of the vertebral column
communicating anteriorly with the small intestine, and the cæca and
posteriorly with the cloaca.
Shape.—The diameter of the large intestine is approximately twice that
of the small intestine. In fowls of average size its mean length is 4.61
inches. The large intestine has sometimes been spoken of as the rectum, or
straight gut.
Structure.—Like the small intestine the large intestine has four coats: an
inner mucous, a submucous, a middle muscular and an outer serous. The
folds of mucous membrane of the large intestine have tubular glands lined
with columnar cells (Fig. 37, A, No. 1).
Function.—The large intestine is similar in function to that of the small
intestine, in that digestion and absorption may take place within it.
The Cæca (Fig. 31, No. 11). Location.—The fowl has two cæca
extending forward from their point of origin at the juncture of the small and
large intestine.
Shape.—The cæca average 7.61 inches in length. They are large in
caliber toward the blind extremity and are constricted near their origin.
Structure.—The parietal coats are continued from the small intestine.
Ebarth has described an elevated body in the cæcum, which is located
about 4 millimeters from the opening and is composed entirely of lymphoid
tissue.

Fig. 37A.—Photomicrograph of a
transverse section of large intestine and
oviduct just anterior to the cloaca,
showing the tubular glands of the large
intestines, mucosa of oviduct with
intervening structures. 1, The tubular
glands of large intestine, or rectum. 2,
Muscular wall of intestine. 3, Wall of
the oviduct. 4, Mucosa of the oviduct.

The cæca are usually partly filled with a soft pultaceous material of a
pasty consistency.
The Cloaca (Fig. 31, No. 13). Location.—The rectum opens by a
circular, valvular orifice into the dilated portion just in front of the anus,
which dilatation is called the cloaca.
Shape.—The cloaca is saccular in shape.
Structure.—The cloaca is divided into two portions, the coprodeumal and
the urodeumal. That portion of the cloaca into which the intestine empties is
called the coprodeum; and the ureter and oviduct empty into the urodeum.
The seminiferous tubules, carrying the semen from the testes in the male
empty in teatlike projections on the cloacal mucous membrane into the
urodeumal portion. The cloacal walls are similar in structure to the large
intestines.
On the dorsal wall of the cloaca between it and the spine, is a small sac,
called the bursa of Fabricius, which has a duct communicating with the
cloaca. The mucous membrane of this sac is thrown into folds and is
studded with glands. The bursa of Fabricius is larger in the young than in
the adult bird. It apparently atrophies as the bird becomes older. When the

bird is four months old this bursa is best developed, and at this age it may
be as large as 2 or 3 centimeters in diameter.
Function.—The function of the cloaca is to give passage way to the
feces, the urine, and the egg and to act as an organ of copulation.
Course of the Food.—The food first enters the mouth, after being picked
up by aid of the beak. From here it passes through the pharynx and first
portion of the esophagus to the crop, without mastication, as the bird is not
provided with teeth. The food is passed from the crop by aid of its muscular
walls as needed; thence through the second portion of the esophagus to the
proventriculus, an expansion in the digestive tube just before it terminates
in the gizzard. The glands of the proventriculus produce a secretion in
which the food is soaked before passing into the gizzard. The gizzard is
provided with strong muscular walls which, by aid of grit, thoroughly
reduce the food to fineness. From the gizzard the food passes through the
first portion of the small intestine, where it is subjected to the action of the
bile from the liver, the pancreatic juice from the pancreas, and of the succus
entericus from the glands of the intestinal wall. The food is then passed into
the cæca. The indigestible portion of the food passes from the cæca through
the large intestine, or rectum, to the cloaca and thence to the external world.
The digestive functions of the bird are very potent and rapid. This
compensates for the waste caused by their extensive, frequent, and energetic
motions, and is in accordance with the rapidity of their circulation and their
high state of irritability.

THE ACCESSORY ORGANS OF DIGESTION

The accessory organs of digestion are the liver, pancreas, and some
anatomists include also the spleen. The first two manufacture fluids
containing ferments which aid in splitting or digesting the food.
The Liver (Figs. 31, 33 and 34). Location.—The liver, hepar, lies
ventrally and posteriorly to the heart. It is related anteriorly with the
diaphragm, inferiorly with the sternum, posteriorly with the gizzard and
intestine, and superiorly with the ovary, oviduct and proventriculus and
laterally with the abdominal wall.
Shape.—The liver is a voluminous deep livid brown gland, soft and
friable in texture. It is divided into two principal lobes, a right and a left.
The right lobe is larger than the left. In the hen of average size the liver
weighs 35 grams. The parietal surface is convex and smooth. The surface
which lies against the viscera is irregularly concave. The visceral surface
furnishes exit for the bile duct and passage for the nerves and blood-vessels.
This part is called the porta.
The left lobe may be cleft from below so deeply as to form two lobes on
that side.
Structure.—Each lobe is covered by a double serous membrane, one
closely adherent, the other surrounding the structure loosely. These tunics,
which are reflections of the peritoneum, are continued from the base of the
liver, over both the anterior, and the posterior surface. The loose layer is
formed by the air cells surrounding the lobes. The thin border of the liver is
usually free.
The two lobes of the liver are connected by a narrow isthmus of liver
tissue. Occasionally there is a bird in which there occurs a lobus Spigelii
located at the posterior of the liver between the two principal lobes.
The apex of the heart sacculates the diaphragm backward, so that part of
this apex lies between the right and the left lobes (Fig. 43, No. 6 and 7). A
ligament, the falciform, extends from the apex of the pericardial membrane,
and attaching it rather firmly to the central connective tissue, or interlobar
ligament. This ligament also has attachments to the inner surface of the

sternum. The broad ligament of the liver is formed posteriorly by a fold of
the peritoneum.
The interlobar, or principal, ligament of the liver is formed by a large
and strong duplicature of the peritoneum, which makes a longitudinal
division in the abdominal cavity similar to the lateral division made by the
thoracic mediastinum in mammals. It is reflected upon the pericardium
from the linea alba and the middle line of the sternum, and passes deeply
into the interspace of the lobes of the liver. It is attached to these lobes
throughout their whole length and connects them below to one side of the
gizzard. The lateral and posterior part of the liver attach to the adjacent air
cells, and the whole viscus is thus kept fixed in its position during rapid and
violent movements of the bird.
The remains of the umbilical veins are traceable within the duplicature of
the membranes forming the septum. These remains thus represent the round
ligament of mammals.

Fig. 38.—Cellular structure of liver, pancreas, and trachea.

A. Liver. 1, Liver cells. 2, Sinusoid. 4, Nucleus of cells.

B. Pancreas. 1, Island of Langerhans. 2, Alveolar cells. 3, Duct.

C. Trachea. 1, Ciliated epithelia. 2, Glands. 3, Hyaline cartilage.

D. Section of wall of ovum at Fig. 57 letter d. 1, Yolk. 2, Granular membrane. 3,
Theca. 4, Blood-vessel.

A microscopic study of the liver of the fowl shows a compact mass of
liver cells polyhedral in shape, with large nuclei (Fig. 38, A). The liver
tissue differs from that of mammals in that there is no clearly outlined
lobular arrangement; neither is the outline of the individual cell so well
marked. The parenchymatous portion is made up of columns of liver tissue.
These columns anastomose and show narrow channels between. They are
best seen in the young chick.
Function.—One of the functions of the liver is to secrete bile. A gall-
bladder, which receives part of the bile secreted by the right lobe of the
liver, is located on the posterior face of this lobe. Extending from this gall-
bladder there is a duct, the cystic duct, which empties into the small
intestine toward the extremity of the second branch of the duodenal loop.
Another duct called the hepatic duct, proceeds directly from the two lobes
of the liver and empties into the intestine just in front of the cystic duct.
The Pancreas (Fig. 31, No. 17). Location and Shape.—The pancreas, an
organ lying in the duodenal loop is a yellowish-white, lobulated gland,
elongated in shape. Its average length in fowls of average size is 4.96
inches, and the average weight about 0.008 pound. The pancreas is divided
into lobes, which in turn are divided into lobules.
Structure.—The pancreas has a supporting connective tissue. The lobules
are made up of small alveolar glands, which are lined with columnar
epithelial cells. The ducts leading from the alveoli are small; these unite to
form larger ducts in which the epithelium is taller. Between the alveoli
throughout the pancreas there are clusters of polyhedral cells which form
the islands of Langerhans. These islands are said to produce an internal
secretion, or hormone, which is absorbed by the blood or lymph capillaries
and thus enters the circulation (Fig. 38, B).
Function.—The function of the pancreas is to secrete a fluid containing
digestive ferments.
The Spleen (Fig. 31, No. 21). Location.—The spleen, or lien, lies in a
triangle formed by the proventriculus, the liver, and the gizzard.
Shape.—It is a reddish-brown body shaped like a buckeye, is small in
size, weighing only about 0.005 pound.
Structure.—The outer surface of the spleen is covered by a reflection of
the peritoneum. After this covering is removed, there is observed a firm,
white, fibrous layer, the cortical portion. This covering sends into the

interior small and large trabeculæ, forming a framework and dividing it into
acini, or compartments. The spaces are filled with a dark red
parenchymatous material called splenic pulp. The framework, in both deep
and surface portions, are found elastic fibers and smooth muscular fibers.
The spleen is essentially a lymphatic organ, its peculiar structure
depending largely upon the arrangement of the blood-vessels. Compact
lymphatic tissue occurs in the spleen in spherical, oval, or cylindrical
collections of closely packed lymphoid cells. These masses are known as
the Malpighian bodies, or splenic corpuscles. They are distributed
throughout the splenic pulp. Each splenic corpuscle contains one or more
small arteries. These extend near the periphery of the corpuscle and more
rarely in the center.
The splenic artery passes in and the splenic veins out at the hilum which
is located on the concave, or attached, side of the spleen. The splenic artery,
upon entering the organ, at once branches, the trabeculæ forming a support
for the vessels.
After the arteries have entered the hilum, as stated above, they divide into
many branches which follow the septa of the connective tissue. At first the
arteries are accompanied by branches of the splenic veins. Soon, however,
the arteries leave the veins and the septa, and penetrate the splenic pulp. In
the splenic pulp the adventitia of the smaller arteries assume the character
of reticular tissue, and become infiltrated with lymphoid cells. This
infiltration forms masses which are called the splenic corpuscles, or
Malpighian bodies. The terminal arteries break up into capillaries, which
still retain an adventitia, and empty into border spaces, or sinuses,
sometimes spoken of as ampullæ. These sinuses in turn empty into
cavernous sinuses of the splenic pulp. From these are finally formed the
venules; and the collections of venules form the splenic veins through
which the blood gains exit from the spleen.
The Abdominal and Pelvic Cavities.—In birds the abdominal cavity is
divided into two smaller cavities by a fibrous septum. The anterior cavity
representing the abdominal contains the liver, and the other representing the
pelvic contains the gizzard, intestines and oviduct.
The Peritoneum and the Mesentery.—The abdominal and pelvic
cavities are lined by the peritoneum. Like all serous membranes this is
composed of a parietal and a visceral portion, which together form a

complete sac, with the organs it covers situated on the outer side. The
peritoneum like other serous membranes consists of a mesothelial and a
submesothelial portion, the cells of the former being arranged in a single
layer. Since a serous membrane is so arranged as to line a closed cavity, and
at the same time to cover its contents, it follows that the entire membrane
must be a closed sac, the mesothelial layer being on the inside; such a sac is
called a serous sac, or cavity. Synovial membranes are also regarded as a
variety of serous membranes. The fold, or layer, of the membrane which
lines the cavity is called the parietal, that which covers the greater part of
the organs contained therein is called the visceral portion; the two surfaces
contacting, and gliding upon each other, are lubricated by a fluid secretion
contained in the sac; hence one use of these membranes is to prevent
friction between the walls of cavities and the organs contained therein.
Serous membranes line the abdominal cavity, pericardium, cavities of the
heart and is continuous throughout the vascular structures.

Fig. 39.—A transverse section of body
of hen through 15, Fig. 34. R, Right
side. L, Left side. 1, Spinal cord. 2,
Esophagus. 3, Trachea. 4, Skin. 5,
Pectoral muscles.

The serous membrane besides covering the external surface of the
viscera, double folds pass from one organ to another, or from an organ to
the parietes of the cavity. These double folds of the peritoneum are known
as ligaments, or as mesenteries. In ligaments the two folds are strengthened
by an interposed layer of fibro-elastic tissue. A mesentery is a broad, double
fold of peritoneum, attached to the abdominal parietes above, and
containing a portion of the intestine in its free or remote extremity. Between
its folds we find blood-vessels, nerves, and lymphatics or lacteals, hence it
permits vascular and nervous communications with the organ attached to it.
The free portion of the small intestine is attached to the free margin of the
mesentery.

THE RELATIONS OF THE VISCERAL ORGANS OF THE
DOMESTIC FOWL

Fig. 40.—Transverse section through
the body of a hen through 14, Fig. 34. R,
Right side. L, Left side. 1, Spinal cord.
2, Esophagus. 3, Trachea near inferior
larynx. 4, Lungs. 5, Pectoral muscles.

Figure 33 shows a fowl with the left abdominal wall and the left thoracic
wall removed. No. 1 in this figure shows the base of the heart in front of the
left lobe of the liver. Above the liver is the proventriculus; above this, the
diaphragm; and above the diaphragm and the base of the heart the left lung
occupying the superior part of the thoracic cavity, and that there is no
distinct pleural sac, as in mammals but that the lung pushes out between the
ribs, thus pressing against the ribs on the inner and the lateral sides. The
gizzard is back of the liver, to the left side of the abdominal cavity, and
beneath and in front of the duodenal loop. The small intestine from this side

is above the gizzard. Supero-anterior to the gizzard is the blind end of the
cæcum. The pancreas is within the duodenal loop.

Fig. 41.—Transverse section through
the body of a hen at 12, Fig. 33. R,
Right side. L, Left side. 1, Spinal cord.
2, Esophagus. 3, Inferior larynx. 4, Base
of the heart. 5, Aorta. 6, Vena cava. 7,
Lungs. 8, Skin. 9, Pectoral muscles.

Figure 34 shows the viscera from the right side after the removal of the
right abdominal and the right thoracic wall. The base of the heart is in front
of the right lobe of the liver. Above these the right lung occupies the upper
part of the thoracic cavity as in the preceding illustration. Just back of this is
the anterior lobe of the kidney. The gall-bladder is observed at No. 9 on the
right lobe of the liver. Just inferior to a longitudinal central line is the
duodenal loop, between the limbs of which is seen the pancreas. Above this
loop the cæca are located. The gizzard is not visible from the right side; on
this side posterior to the liver is the small intestine. Superior to this at No. 7
the rectum.

The relative position of the visceral organs in the median line is observed
in Fig. 35. No. 1 of this figure shows the stump of the first portion of the
esophagus, and No. 2, the left wall of the crop. Following this, and located
just below the vertebræ is the second portion of the esophagus. The major
portion of the crop is located on the right side.

Fig. 42.—Transverse section through
the body of a hen at 11, Fig. 33. R,
Right side. L, Left side. 1, Spinal cord.
2, Vertebra. 3, Spinous process of
vertebra. 4, Lungs. 5, Esophagus. 6,
Pericardial sac. 7, Sectioned surface of
heart. 8, Auricle of heart. 9, Blood clot
in right auricle. 10, Section of sternum.
11, Pectoral muscles.

It will be noted that the second portion of the esophagus passes over the
base of the heart and the superior part of the liver, and then terminates in the
proventriculus. The proventriculus extends downward and empties into the
gizzard. This organ lies antero-laterally to the gizzard, supero-posterior to
the liver, and to the left of the spleen. The spleen lies in a triangle formed
by the liver, the proventriculus, and the gizzard. The heart is noted to lie

supero-anterior to the liver, and between the anterior portion of the fissure
formed by the right and the left lobe. The ovary is located back of the
diaphragm at the anterior end of the kidney and below the inferior surface
of the bodies of the vertebræ. The bulk of the floating portion of the small
intestine is located above the gizzard.

Fig. 43.—Transverse section through
the body of a hen at 13, Fig. 34. R,
Right side. L, Left side. 1, Spinal cord.
2, Body of vertebra. 3, Superior spinous
process of vertebra. 4, Lungs. 5,
Esophagus. 6, Heart. 7, Right and left
lobes of liver. 8, Sternum. 9, Skin. 10,
Pectoral muscles.

A transverse anterior section of a normal laying hen is shown in Fig. 39,
the section being made at 15 of Fig. 34. At this point the esophagus lies
centrally and above the trachea. Figure 40 shows a transverse anterior
section through the thoracic region at 14 of Fig. 34. At this point the
esophagus is slightly to the right of and is superior to the trachea. At this
level the apex of the lung is sectioned. This is in the region of the cervical
air-sac. Figure 41 shows a posterior section at 12 of Fig. 33. The esophagus

here is above and to the right of the inferior larynx, and directly below and
between the lungs. The inferior larynx is above the base of the heart.
Figure 42 shows a transverse anterior section made at 11 of Fig. 33. It
shows that at this level the esophagus is centrally located and passes over
the base of the heart. The heart occupies the lower portion of the thorax and
the lungs the upper. Figure 43 shows a photograph of a transverse anterior
section of the body made at 13 of Fig. 34. At this level the apex of the heart
lies within the anterior fissure of the liver. The sectioned portion of the heart
shows the lower portion of the ventricle.

Fig. 44.—Transverse section through
the body of a hen at 12, Fig. 34. R,
Right side. L, Left side. 1, Spinal cord.
2, Articular surface of vertebral
segment. 3, End of rib. 4, Lungs. 5,
Proventriculus. 6, Liver showing
Glisson’s capsule. 7, Sternum. 8,
Pectoral muscles. 9, Skin.

Fig. 45.—Transverse section through
the body of a hen at 10, Fig. 33. R,
Right side. L, Left side. 1, Spinal cord.
2, Body of vertebra. 3, Lungs. 4, Ova. 5,
Proventriculus. 6, Liver. 7, Sternum. 8,
Skin. 9, Pectoral muscles.

In this figure the lungs show, on the sectioned surface, the ends of some
of the larger bronchi. The esophagus is located above the heart. Showing
the relations of the visceral organs back of the heart girdle, photograph
number 44, gives an anterior section made at 12, Fig. 33. The lungs are
spread out occupying the posterior thoracic region and below at No. 10 is
the diaphragm. The diaphragm does not appear to have that rigidity and
firmness of position as in mammals. It is rather rudimentary. Below the left
lung and above the left lobe of the liver is the proventriculus. Note that the
viscus is empty and that the mucous membrane is thrown into folds. At this
point the liver occupies much of the abdominal cavity. Figure 45 is a view
of an anterior section made at 10, Fig. 33. In this section the lungs are
decreasing in caliber. The liver occupies much of the space in the lower
right abdominal quadrant, and above and to the right is the ovary with many
of the ova developing yolks. Below No. 4 which is a developing yolk, is the
proventriculus. Figure 46 is a view of an anterior section made at 9, Fig. 33.
At this level are shown sectioned surfaces of the kidneys, which lie on
either side of the spinal column. Below the spinal column and occupying

the left upper quadrant is the ovary containing ova in the process of
developing yolks. To the right is the sectioned surface of one of the cæca
and below this and on the right side is the sectioned ends of many of the
loops of the floating portion of the small intestine. Occupying the left lower
quadrant is the sectioned surface of the gizzard and on the abdominal floor
and to the right of the gizzard, the posterior end of the right lobe of the
liver.

Fig. 46.—A transverse section through
the body of a hen at 9, Fig. 33. R, Right
side. L, Left side. 1, Spinal cord. 2,
Vertebra. 3, Kidneys. 4, Ovary. 5,
Cæcum. 6, Small intestine. 7, Gizzard.
8, Right lobe of liver. 9, Skin. 10,
Pectoral muscles.

THE RELATIONS OF THE VISCERAL ORGANS OF THE
BABY CHICK
There is approximately 47 per cent. of the yolk retained in the abdominal
yolk sac of the baby chick at hatching. Figure 47 shows a photograph of a
longitudinal section through a baby chick. This figure shows all the
posterior portion of the abdominal cavity occupied with abdominal yolk.
The abdominal viscera are pushed forward, and as the yolk is gradually
absorbed the visceral organs gradually occupy their normal position.

Fig. 47.—An antero-posterior section through the body of a baby chick just
hatched. 1, Abdominal yolk sac. 2, Gizzard. 3, Liver. 4, Heart. 5, Intestines. 6,
Spinal cord. 7, Cerebrum. 8, Cerebellum. 9, Fat in the post-occipital region. 10,
The thymus gland.

Fig. 48.—Transverse sections of the
body of a baby chick at hatching. R,
Right side. L, Left side.

A. A transverse section at A, Fig. 50. 1,
Spinal cord. 2, Esophagus. 3, Entrance
to thorax. 4, Stubs of the wings.

B. A transverse section at B, Fig. 50. 1,
Spinal cord. 2, Esophagus. 3, Lungs. 4,
Heart.

C. A transverse section through the body
at C, Fig. 50. 1, Spinal cord. 2, Lungs.
3, Esophagus. 4, Liver. 5, Heart.

D. A transverse section at D, Fig. 50. 1,
Spinal cord. 2, Proventriculus. 3, Liver.
4, Gizzard. 5, Intestine. 6, Kidneys. 7,
Gall-bladder.

Fig. 49.—Transverse section through
the body of a baby chick.

E at E, Fig. 50. 1, Spinal cord. 2,
Kidneys. 3, Gizzard. 4, Intestines. 5,
Unabsorbed yolk. 6, Stubs of legs.

F. A section at F, Fig. 50. 1, Spinal cord.
2, Kidneys. 3, Intestine. 4, Unabsorbed
yolk.

G. A section at G, Fig. 50. 1, Anus. 2,
Umbilicus.

A section through this body Fig. 47 at A is shown in Fig. 48, A. At this
point the esophagus appears below the vertebral column. Figure 48, B, a
section through the body at Fig. 47, B, shows the apex of the lungs. In a
median line and below the lungs is the esophagus. Note the mucous
membrane thrown into folds. Here the heart is sectioned, showing both
auricles and both ventricles. This is a view looking forward. Figure 48, C, is

a view of a posterior section made at Fig. 47, C. It shows the same relations
of the esophagus and lungs, but shows at this level both the right and the
left lobe of the liver. Between these lobes we note the sectioned apex of the
heart. Figure 48, D shows a posterior section at Fig. 47, D. At this level the
kidneys are above and infero-laterally to the spinal column. The intestines
are below the kidneys; and on the left side, between the kidneys and left
lobe of the liver, and near the abdominal wall, is the proventriculus.
Occupying the major portion of the inferior abdominal cavity are the right
and the left lobe of the liver, and between these the anterior border of the
gizzard. Note the gizzard sitting at an angle inclining toward the left side.
Figure 49, E shows a section at Fig. 47, E. Here the gizzard occupies the
left lower abdominal quadrant. To the right are the intestines; and directly
above the gizzard is a small portion of the anterior end of the abdominal
yolk sac. Infero-laterally are the kidneys. Figure 49, F, shows the kidneys
similarly located as in the preceding; and just below is the rectum
suspended by the mesentery. The rest of the cavity is occupied by the
abdominal yolk.

THE URO-GENITAL SYSTEM

The uro-genital apparatus, or apparatus uro-genitalis, consists of two
groups of organs: the urinary and the genital. The former elaborate and
remove the chief excretory fluid, the urine; and the latter serve for the
formation, development, and expulsion of the products of the reproductive
glands.

THE URINARY APPARATUS (Fig. 50 and Fig. 51).

The urinary apparatus of the bird consists of two kidneys, from each of
which a ureter extends and empties into the cloaca.
The Kidneys. Location.—The kidneys are located in excavations in the
pelvic roof. They are related internally with the posterior aorta and vena
cava, supero-internally with the lumbo-sacral vertebræ and superiorly and
supero-externally with the ilium. The abdominal visceral organs lie below
the kidneys. The kidneys are external to or above the peritoneum.
Shape.—In the fowl of average size the kidneys are 2½ inches long and
are made up of three irregular lobes. The anterior lobe is usually the largest
and the middle the smallest. The anterior border of the first lobe is located
opposite the last true dorsal articulation. The anterior lobe is called the
anterior pelvic or ilio-lumbar lobe, the middle the middle pelvic or ilio-
sacral lobe, and the posterior the posterior pelvic lobe.
Structure.—The whole kidney has a fine transparent covering. The dark,
brownish-red parenchyme can be seen through this membrane. It has a
blood vascular system and a urinary tubular system. The larger arteries, the
veins, and the nerves pass between the lobules, and the smaller vessels
between the tubules. These form fine network or plexuses. The lymphatic
vessels are very few, and are mainly found on the surface. The kidneys are
pierced in their posterior third by the external iliac artery and at about its
middle by the venous branches forming the posterior vena cava.
The lobes are made up of lobules, which are plainly perceptible from the
external surface. Each lobule is apparently a unit within itself. It receives its
blood supply from small branches of the renal artery and is made up of a
cortical or peripheral portion which contains the glomerules (Fig. 52, A) and
a medullary portion, which is made up of tubules, or urinary canals,
arteries, veins, and nerves.

Fig. 50.—Photograph showing spinal cord and relative positions of the kidney,
lung and heart. 1, Heart. 2, Lung. Note the indentations made by the ribs. 3, The
anterior, middle and posterior lobes of the kidney. The lobules are plainly visible.
4, The lumbo-sacral segment of the spinal cord. 5, Terminal cord filament. 6, The
cervico-dorsal segment of the spinal cord. 7, The brachial nerve plexus. 8 and 9,
The lumbo-sacral plexus. 8, The ischiadic nerve. 9, The lumbar nerves.

The urinary canals are divided into two kinds, namely, the outer and the
inner tubular systems. The outer canals, called the tubulæ uriniferi
corticalis, are very small in caliber and are located in the lobules. The renal
artery (Fig. 53, No. B, 3) breaking up into arterioles in the kidney, and
finally reaching the cortical portion of the lobules, form capillary plexuses
in the shape of minute spheres, which are the glomerules (Fig. 53, No. C, 3
and B, 5). Around each glomerule there is formed a capsule called
Bowman’s capsule, which is the beginning of the uriniferous tubule. This
entire mass is called the Malpighian body, or renal corpuscle. This capsule
then extends as the urinary, or secreting tubule, being at first constricted,
then convoluted, and terminates into a second portion, the descending limb
of Henle. This portion of the tubule becomes constricted. It then forms the
loop of Henle and ascends as the second portion, or second limb of Henle,
which is again of greater diameter. The top of the secreting tubule is slightly
wavy and empties into the collecting tubule along with many others. These
collecting tubules in turn merge into large tubules which finally empty into
the ureter (Fig. 53, No. 14). These collective bundles correspond to the
pyramids of the kidneys of mammals.

Fig. 51.—The kidneys. 1a, The posterior. 1b, the middle and 1c, the anterior
lobes of the kidney. 2, The posterior aorta. 3, The external iliac or crural artery.
4, The ischiadic artery. 5, The sacralis media artery. 6, The ureter which empties
into the cloaca at 7. 8, The external iliac vein. 9, The internal iliac vein. 10, The
iliacus communis.

Fig. 52.

A. Photomicrograph of a section of a
kidney showing three lobules. 1,
Cortical portion of lobule showing
glomeruli. 2, The central or medullary
portion of the lobule. 3, The outer
surface of the kidney.

B. Salts from the urine of a hen. 1, Uric
acid crystals. 2. Sodium urate crystals.

Fig. 53.—The renal structure.

A. 1, Capillary blood-vessel. 2,
Descending limb of Henle. 3, Collecting
tubule. 4, Ascending limb of Henle.

B. 1, Branch of renal artery. 2, The
descending or medullary branch. 3, The
ascending branch. 4, The arteriole
taking part in the formation of the
glomerule. 5, The glomerule. 6,
Bowman’s capsule. 7, Blood-vessel
extending from the glomerule. 8, The
vein of the medullary part of the lobule.
9, The neck. 10, The convoluted tubule.
11, The descending limb of Henle. 12,
Henle’s loop. 13, The ascending loop of
Henle. 14, The collecting tubule.

C. 1, Section through a convoluted
tubule. 2, Bowman’s capsule. 3, The
glomerule.

The neck of the uriniferous tubule as it emerges from Bowman’s capsule
is short and narrow and is lined with a few cuboidal cells. Toward the

glomerular end the cells are of a transitional form gradually merging into
the flat squamous type peculiar to Bowman’s capsule. The first convoluted
tubule is lined with irregular cuboidal or pyramidal epithelial cells. The
descending limb of Henle’s loop is narrow and is lined with a simple layer
of flat epithelial cells. In the loop the epithelium changes from the flat type
in the descending limb to the cuboidal in the ascending limb. The ascending
limb of Henle’s loop again becomes broader and is lined with low cuboidal
cells. The second convoluted, or tortuous, tubule is lined with low cuboidal
cells as are also the collecting tubules. The collecting tubules originate from
every part of the internal substance of the lobules, and extending to the
gyrations, uniting in the pinniform structure and traversing to the margin of
the lobules, following along the uneven surface, infero-laterally and toward
the median body line, finally empty into the ureter.
There are many arterial branches given off from the arteria renalis. The
arteries which supply the kidneys are given off from the posterior aorta and
ischiadic artery. As soon as these arteries enter the kidney they break up
into two systems. One system supplies the kidney substance with
nourishment in the form of nutrient blood; the second system supplies the
glomerules with what may be considered functional blood (Gadow). The
second system of arteries branches into the small arteria interlobularis,
which pass between the lobules of the kidneys where they give off side
branches which penetrate the cortical portion of the lobules and form the
capillary plexus, the glomerule.
The arteriole that enters into the structure of the glomerule is lined with
endothelial cells and is surrounded by a few muscle fibers and a fine
network of connective tissue. The vessel that carries the blood away is
similarly constructed.
Function.—In the glomerules the liquid portion of the urine is filtered out
of the blood, which urine flows through the uriniferous tubules and passes
from the kidney through the ureter. In the cubical cells are extracted the
solid portions of the urine which also pass through the tubules with the
liquid. The urinary secretion, as found in the ureter, does not contain much
liquid, but, on the contrary, is made up of a pasty material consisting of salts
which are, for the most part, uric acid crystals and sodium urate (Fig. 52,
B). This material becomes hard, like cement, soon after being exposed to

the atmosphere. This secretion may be noted as a whitish pasty material on
the outer parts of the feces, or droppings, voided by the birds.
The Ureter. Location.—The ureter extends along the inferior surface of
the kidney. It has its origin near the anterior extremity of the kidney, and
passing posteriorly the entire length of the kidney receives tributary
collecting tubules, and terminates in the upper wall of the cloaca in the
urodeumal portion.
Shape.—The ureter gradually enlarges in diameter until it reaches the
posterior border of the kidney, and then maintains about the same caliber
throughout the rest of its course.
Structure.—The ureter wall is made up of three coats as follows: mucous,
muscular and fibrous.
Function.—The ureters serve as a passage way for the urine from the
kidneys to the cloaca.

THE MALE GENERATIVE ORGANS (Fig. 54)

The male generative organs in the fowl consist of two testicles and an
excretory apparatus, the vas deferens, for each.
The Testicles. Location.—The testicles are located in the sublumbar
region of the abdominal cavity, behind the lungs, below the anterior
extremity of the kidneys, and opposite the last three ribs.

Fig. 54.—The pelvic organs of a cockerel. A, Testes. B, Rectum. C, Cloaca. D,
Vas deferens. E, Kidney. F, Adrenal gland. G, Lungs. H, Ureter.

Shape.—The testicles are ellipsoid in shape; their size varies with the
different species of birds. The two in the same bird are usually of the same
size, though one testicle may be slightly larger than the other. In a summary
of a large number of weights of the testicles of ten months old cockerels,
the average weight was 0.021 pound each. The average measurements were
2 inches in the major diameter and 1 inch in the minor diameter. In the
cockerel before sexual maturity, which is denoted by the male bird’s
crowing, the testicles are very small. They resemble, in shape, a navy bean
and are yellowish-white in color.
Structure.—The testicle is surrounded by a thin fibrous capsule, which,
in the mature cock, is very vascular. This capsule sends into the interior of

the gland, septa which form the framework, or supporting structure. This
framework forms the spaces in which are located the glandular substance.
The glandular portion consists of the tubuli seminiferi, which are lined with
cubical cells. The framework supporting these tubules gives passage to
arterial branches of the spermatic artery, which furnish an abundant blood
supply; the framework also supports the veins returning the blood from the
testicle. The seminiferous tubules end in blind extremities in the
epididymus or globus minor, and unite in the seminiferous canals. All
arteries, veins, lymphatics, and seminiferous tubules enter or leave through
the globus minor at the attached portion of the testicle. The epididymis is
made up largely of convoluted tubules which are the continuation of the
secreting tubules of the globus major. The walls of the tubules of the globus
minor become thicker and are provided with smooth muscle cells in
addition to the connective tissue and endothelial lining. The convoluted
tubules empty into the vas deferens. The epididymus is covered by the
fibrous capsule; which corresponds to the tunica albuginea of mammals and
may be considered as a reflection or modification of the visceral
peritoneum.
The substance of the testicle is very soft; in fact, it may be said to be of
the consistency of encephaloid material. It is made up of secreting tubules
in which are found the spermatozoa; it also contains cells which produce an
internal secretion, or hormone. There is also produced some fluid in which
the spermatozoa float, the whole material manufactured constituting the
semen.
The spermatozoa of the fowl are provided with long cylindrical bodies,
which may be straight or wavy (Fig. 55, A). The body of the spermatozoon
is obtuse anteriorly, and posteriorly, tapers into a filimentary tail, or
flagellum, of varying length, by the aid of which the spermatozoon moves
about in the fluid.
The histological structure of the testicles of the baby chick at hatching is
approximately one-half white fibrous connective tissue. The seminal
tubules are small and widely distributed among the connective tissue. The
cells of these tubules possess rather large nuclei, round in shape, with linin
network and chromatin granules, typical of resting germ cells. As the bird
develops the testicles grow, the seminal tubules become larger, and the
amount of connective tissue correspondingly less.

Fig. 55.

A. Spermatozoa of a cock. a, The
spermatozoa. b, The head. c, The tail.

B. The oviduct of a hen removed. A, The
oviduct. B, The superior ligament. C,
The inferior ligament. Note the oviduct
thrown in folds and the anastomosing
blood-vessels.

In addition to the tubules, the spermatogenic cells, and the connective
tissue, there is also in the testicles more or less fat. There is a small amount
of connective tissue between the seminiferous tubules, in which locations
there are also clusters of polyhedral cells, with round nuclei, others are the
interstitial cells.
The Vas Deferens (Fig. 54, D). Location and Shape.—Extending from
the epididymus, is the vas deferens which runs backward on the infero-
internal surface of the kidney and to the outside of the ureter. It is very

tortuous passing on the infero-lateral surface of the kidney in company with
the ureter and becoming somewhat expanded posteriorly it terminates in the
upper wall of the cloaca in a rather small papilla located in the uro-genital
portion of the cloaca anterior to the mouth of the ureter. This papilla is the
organ of copulation and in ducks is very large, and spirally elongated, and
retractile forming a kind of penis. The papilla is traversed by a furrow on
the upper surface through which the semen flows.
Structure.—The vas deferens is covered and supported by the
peritoneum. Its wall is made up of a fibrous structure in which may be
found smooth muscle fibers. The wall does not possess glands. It is lined
with columnar epithelium. The posterior end is expanded and terminates
into a papilla. The base of the papilla is surrounded by a plexus of arteries
and veins, which serve as an erectile organ during the venereal orgasm,
when the fossa of the turgid papilla is everted, and the semen brought into
contact with the similarly everted orifice of the oviduct of the female, along
which the spermatozoa pass by undulatory movements of their ciliary
appendage, or tail.

THE FEMALE GENERATIVE ORGANS (Fig. 56)

The female generative organs consist of one ovary and an oviduct.
Location.—The ovary is located similarly to the testicles of the male
bird, in the sublumbar region of the abdominal cavity, just at the anterior
end of the kidneys, posterior to the lungs, and slightly to the left of the
center.
Shape.—In the pullet the ovarian mass appears somewhat like a bunch of
grapes, being made up of from 3500 to 4500 small, whitish spheres, which
represent the undeveloped ova, and which in the active state are developed,
one by one, into yolks with their blastoderms. From the blastoderm the
fetus may later be developed. In the active ovary of the laying hen the
ovarian mass is of considerable size, as it contains ova in different stages of
development. Only one ovum is completely developed at a time, though
occasionally there may be only a few hours between the maturity of
successive ova. The ova receives nourishment from the blood-vessels of the
capsule, which vessels are branches of the ovarian artery.

Fig. 56.—Functionating female generative organs of a hen. 1, Ova in process of
formation of yolk. 2, Stigmal line at which point the capsule ruptures when
ovum is mature. 3, The funnel end of the oviduct. 4, The oviduct torn loose and
laid to one side, the albumin-secreting portion. 5, The shell membrane secreting
portion. 6, The albumin. 7, The yolk. 8, The shell-secreting portion. 9, The
cloaca. 10, The rectum.

Structure.—The ovary contains very vascular cellulofibrous tissue. The
ovum as it develops is attached to the ovarian body by means of a delicate
white fibrous pedicle. When the yolk is mature it escapes from the
enveloping fibrous capsule by a cleavage of the capsule. The cleavage line
is called the stigmen (Fig. 56, No. 2). The yolk is surrounded by a very
delicate membrane called the vitelline membrane. The empty sac now
shrinks and finally disappears.
The Egg.—The principal divisions of the egg are the yolk, the albumin
outside of the yolk content, the shell membranes and the shell (Fig. 58). As
stated, the yolk is formed in the ovary, leaving the other three portions to be
formed in the oviduct.

Fig. 57.—Section through the ovary of
the hen. a, The ova. d, An ovum
beginning to receive deposits of yolk
material. c, Ova farther advanced in
yolk formation.

The albumin may be subdivided into, first, a thin layer of albumin lying
close around the yolk; second, a thick layer of albumin lying at the outer
periphery; and third, a modification of the albumin called the chalazæ. The
chalazæ are twisted, dense cord-like structures at either pole of the yolk,
one end of which is adherent to the vitelline membrane and the other to the
inner membrane surrounding the albumin. The chalazæ thus act as stays to
this structure, which is carrying a delicate burden, the blastoderm.
The shell membrane consists of two layers, an inner delicate, and an
outer thicker layer. When the egg is just laid these two membranes are in all
parts closely adherent to each other, and the egg content completely fills the
shell cavity. As soon as the content cools there is a slight contraction; the
two shell membranes separate at the large end of the egg, forming an air
cell which gradually enlarges as the evaporation of liquid through the pores
of the shell takes place.

Fig. 58.—A diagram of the parts of the egg. a, The blastoderm. b, The shell. c,
The outer shell membrane. d, The inner shell membrane. e, The air-sac at the
large end of the egg. f, The albumin. g, The chalaza. h, The yellow layers of yolk.
i, The white layers of yolk. k, The flask-shaped portion of white yolk. l, The
vitelline membrane.

The shell consists of several layers. Three are easily distinguishable: first,
an inner mammillary layer, consisting of minute conical deposits of
calcareous material; second, a middle spongy layer, composed of a thick
network of fibers; third, an outer delicate, cuticle-like structure. In certain
breeds of poultry a pigment may be added; for example, in ducks a pea
green, in turkeys a spotted brownish material, and in fowls pink and various
shades of brown. The egg shell is porous to admit the free exchange of air
during the process of incubation.
An average sized hen egg weighs about 2 ounces, of which 11 per cent. is
shell, 32 per cent. yolk, and 57 per cent. white. The principal chemical
constituents of the egg are as follows: ash, or mineral matter, 9 per cent.;
fat, or hydrocarbon, 9.3 per cent.; proteids, or nitrogenous matter, 11.9 per
cent.; and water, 65.5 per cent. There is apparently no constant proportion
of weight between the yolk and albumin. There is also a variation in the
weight of the shell due to its variation in thickness.

In an examination of ten eggs of average size, the yolk constituted 31 per
cent. of the total weight of the egg.
The following is the result of the analysis of twelve eggs of average size.
This analysis included the shell and all other parts taken together.[6]
6. The analysis was made by D. M. McCarty, chemist, Animal Industry Division, North Carolina
Experiment Station.

Moisture 64.25 per cent.
Dry matter 35.75 per cent.

100.00 per cent.

Parts per hundred including shell

Protein 10.2500
Fat 10.6200
Phosphorus .3020
Calcium .6080
Magnesium .0985
Iron .0103
Sulphur .3950
Chlorine .1506
Potassium .0103
Sodium .2000

The Oviduct.—The three separate and distinct portions of the egg,
albumin, shell membranes, and the shell, are constructed in different parts
of the oviduct.
Location.—The oviduct of the hen extends along the left side of the
bodies of the vertebræ, and the roof of the pelvic cavity and lies dorsal to
the abdominal air-sac. It extends from the posterior border of the ovary and
empties into the cloaca (Fig. 56, No. 3 and 8) through a transverse slit.
Shape.—In a well-developed Plymouth Rock pullet, but one whose
reproductive organs have never become active, the oviduct is about 4½
inches long; in the fully developed and active state it is from 18 to 20 inches
long, and in a collapsed state about ½ inch in diameter. It is held in position
by two ligaments, a dorsal and a ventral (Fig. 55, B) to be described later.

The oviduct is tortuous in its course, forming three principle convolutions
before reaching the cloaca, and like the ovarian mass, in its active state,
pushes the abdominal viscera downward and toward the right side.
Structure.—The oviduct consists of three coats: first, the serous, located
on the outside, which is a reflection of the peritoneum; second, the
muscular middle tunic; third, the mucous coat, which in a resting state is
thrown into folds.

Fig. 59.—The active oviduct of a hen
laid open. 1, The ovary. 2, The funnel. 3,
The albumin-secreting portion. 4, The
isthmus. 5, The shell=gland portion. 6,
The vagina. 7, The superior ligament. 8,
The inferior ligament.

Parts of the Oviduct.—The parts of the oviduct are as follows: the
funnel, the albumin-secreting portion, the isthmus, the shell-gland portion,
or uterus, and the vagina (Fig. 59).

Fig. 60.—The mucous lining of the oviduct.

A. Transverse section of the oviduct wall in the region of the neck of the funnel
showing primary and secondary folding of the epithelium (after Surface).

B. Showing the type of gland cells of the funnel region.

C. Transverse section through the wall of the uterus showing the deep folds.

D. Section from the albumin-secreting portion showing the opening of a tubular
gland and also showing the character of the cells.

The funnel is the trumpet-shaped portion, the ostium tubæ abdominale,
whose mouth or fimbriated opening faces the ovary, and lies ventrally to
receive the ovum, or yolk, as it is discharged from the ovary. Its thin wall,
expanded in the anterior portion, is provided with fimbriæ-like projections.
This funnel-shaped portion soon converges to form a constricted portion.
This portion of the active oviduct is from 3 to 4 centimeters long. The
mucous membrane occurs in folds forming low longitudinal spiral ridges
(Fig. 60, A). The fimbriæ are continuous with the dorsal and the ventral
ligament of the oviduct; and from this point, where the ridges of the mucous
membrane are almost nil, they gradually increase in height as they extend
down the tube. These ridges are continued in those of the second, or
albumin-secreting portion (Fig. 60, D). At this point they increase in height
very rapidly. Here the bundles of muscular fibers of the middle coat are thin

and distributed among bundles of connective tissue. The muscular fibers
consist of two layers, an outer longitudinal and an inner circular. At places
in this portion the inner bundles may be noted to extend longitudinally. In
embryological development the epithelial layer has an origin different from
the outer layers of the oviduct. In the fetal development the Müllerian duct
arises as a thickening along the Wolffian body just ventral to the gonad.
This Müllerian duct is at first a solid cord of cells. It later develops a lumen,
and grows posteriorly until it connects with the cloaca. At the time of this
posterior growth, mesenchyme cells migrate in from the surrounding tissue
and form a layer about the duct. From this layer of mesenchyme cells there
are developed the outer layers of the oviduct, which layers later develop the
muscular structure and the connective tissue. The epithelium and its
derivatives, which represent the glandular structures, are formed from the
walls of the old Müllerian duct. Thus the two sets of tissues, having
different origins, likewise have different functions. The epithelium is
concerned entirely with secretion, and the derivatives of the mesenchyme
are concerned with supporting and muscular function.
To summarize, six layers of tissue occur in the
funnel region, namely, an outer serous covering,
an outer longitudinal muscular layer, a layer of
connective tissue, an inner circular layer, a second
layer of connective tissue, and an inner mucous
layer. The mucous layer is made up of glands, as
follows. The unicellular glands occur between the
ciliated cells of the epithelium. These glands are
found only in the posterior half of this division of
the oviduct. The glandular grooves are made up of
an accumulation of gland cells at the bottom of the
grooves between the secondary folds of the
epithelium. These are found in all parts of this
division except the extreme posterior part. In the
posterior part we find the third type of glands, the
tubular variety. Fig. 60. A.—The
The second division of the oviduct, as stated mucous lining of the
above, is the albumin-secreting portion. The oviduct.
funnel division gradually merges into the second
portion. These two portions are distinguishable E. Section of the

from each other. The walls of the albumin- epithelium from the
secreting portion are much thicker and the vagina showing
longitudinal ridges are higher. This section is the unicellular glands.
longest of the five divisions, measuring from 40 to
42 centimeters in length, or more than half the F. A section from the
length of the oviduct. The albumin division isthmus showing
terminates rather abruptly into the third division, opening of a tubule.
the isthmus (Fig. 59, A).
It is probable that the secretion of albumin is not confined to the cells of
the second division; yet we are safe in saying that the major portion is
formed here. The folds of mucous membrane in this division are thicker and
higher than in the funnel, due to their containing cells of the high columnar
type, and to the fuller development of the glands which are of the tubular
variety. The muscular layer is heavier, and therefore the muscular power to
force along the tubes’ contents is greater. In the formation of the mucous
folds we find, in transverse sections, that the central core is made up of
connective tissue which carries blood-vessels and nerve filaments, as in
other similar glandular structure. The epithelium contains glandular cells of
two varieties, namely, the ciliated, columnar variety, and the unicellular,
goblet variety (Fig. 36, No. B, 2). These two kinds of glandular cells are
rather evenly distributed throughout the epithelium of this section of the
oviduct. The unicellular gland cells are more numerous at the mouths of the
ducts leading from the tubular glands. The nuclei of the ciliated cells are
oval and lie near the middle of the cells or a trifle toward the base from the
middle. The protoplasm of the cells is finely granular. Strong cilia in
considerable number surmount each cell. In some cases the goblet or
mucous cells have pushed apart the ciliated cells, and their prolongations
extend farther than the surface of the ciliated cells. The nuclei of the goblet
cells are round, and lie nearer the proximal end than those of the ciliated
cells.
The third division of the oviduct, the isthmus, continues from the
albumin-secreting portion and terminates in the expanded portion called by
some anatomists, the uterus. Toward the posterior end of the albumin-
secreting portion the longitudinal folds of mucous membrane become
lower, making, at the juncture of this and the isthmus, a clear fine of
demarcation. For a distance of 2 or 3 centimeters the folds are low, after

which they gradually become higher, but never reach the height or thickness
of those in the albumin-secreting portion.
The clear-cut line between the albumin-secreting portion and the isthmus
is partly due to a zone in which the long tubular glands are lacking. The
core of the folds of mucous membrane in this zone contain much more
connective tissue. The cells are both ciliated and unicellular. The rest of the
histological structure of the isthmus is the same as that of the albumin-
secreting portion.
The function of the isthmus is to secrete, or to form, the shell membrane,
the membrana testacea.
The fourth division of the oviduct is the uterus, or the shell-gland portion
(Fig. 60, C). There is no clear line of demarcation between the isthmus and
shell-gland portion, the walls gradually expanding. In this region the folds
of mucous membrane become leaf-like and of considerable length,
extending into the lumen, thus affording a greater cellular surface. The same
coats of the duct are present here as in other parts; but the outer longitudinal
muscular layer is thicker and possesses more strength. The quantity of
connective tissue is about the same. The glands are of a tubular type and the
same two varieties of epithelial cells are found here as elsewhere, namely,
the ciliated high columnar and the unicellular mucous variety.
In the active glandular cells of the shell-forming region the nuclei are
small, dark staining, and lie toward the center of the cell. The chromatin
granules and nucleoli take on a comparatively deep basic stain, but they do
not show the intense stain found in the albumin and the isthmus region. The
cytoplasm of the uterine tubular glands does not present as heavy a granular
appearance as that of the albumin portion. These cells are diffusely
granular, the granules appearing of one size and taking the stain faintly. The
function of this portion is to secrete, or form, the hard calcareous covering
which has been described at the beginning of this section.
The fifth division of the oviduct is the vagina. There is located, at the
juncture of the shell-gland portion with the vagina, a strong sphincter
muscle. The vagina is that constricted portion of the oviduct extending from
this muscle to the cloaca. The mucous membrane forms low narrow folds
with secondary folds, which appear continuous with those of the shell-gland
portion. The core of these folds is composed of connective tissue. The
vagina in the hen of average size measures from 12 to 13 centimeters long

(Surface). The inner or circular muscular layer is well developed; it is much
thicker than in any other part of the oviduct. This extra development gives
the power necessary to successfully expel the egg. The outer longitudinal
layer is not so well developed; its bundles are scattered throughout the
connective-tissue layers. The egg is caused to move along in the oviduct by
a successive series of contractions of the circular muscular fibers posterior
to it. There are no tubular glands in this portion, but a simple layer of high
ciliated columnar epithelium, and some goblet, or mucous cells. The cells
on the surface generally are long and slender; in the grooves between the
mucous folds the cells are shortest, reaching their greatest length at the tops
of the folds.
The function of the vagina is the secretion, or formation, of the outer
shell cuticle commonly called the bloom, and also in certain breeds, as
indicated above, the tint.
The cloaca furnishes a passage way from the vagina to the external world
by way of the anus. The walls of the cloaca contain glands.
The Ligaments of the Oviduct.—It is held in position by two ligaments,
one dorsal and one ventral. The dorsal ligament of the oviduct is formed by
a double layer of peritoneum with a very small amount of connective tissue
interposed. The peritoneum is also reflected over the oviduct. The ventral
ligament of the oviduct is narrower than the dorsal, but is similarly
constructed. Both ligaments are rather veil-like in appearance. During the
first four or five months of the growth of the young female fowl the
development of the oviduct and its ligaments is in proportion to that of the
body. With the elongation that takes place about the time of functionation,
as described above, the ligaments enlarge in proportion to the enlargements
of the oviduct. The dorsal ligament maintains a line of attachment to the
body wall from the caudal end of the body cavity to the fourth thoracic rib.
The ventral ligament elongates only slightly during this developing period.
It becomes thicker and stronger and early develops a muscular coat. It also
grows in width except at the caudal end. At this point the ligament is simply
a mass of muscular tissue of the smooth or involuntary type. These
ligaments are fan-shaped.
The muscle fibers of the dorsal ligament of the laying hen, have their
origin in a line near the medial side of the dorsal margin. At this point the
bundles of fibers are quite thick, but are spread out thinly toward the margin

of the oviduct. Frequent anastomoses are noted. The muscular fibers
become continuous with the circular ones of the oviduct.
The ventral ligament of the oviduct of the laying hen is largely a
muscular cord 3 to 6 centimeters in diameter. The caudal end is thicker,
becoming gradually thinner toward the anterior portion. The bundles of
muscular fibers extend toward the oviduct blending with the circular fibers
of that viscus. The ligaments terminate anteriorly in such a manner that they
aid in forming the serous ovarian pocket, which guides the yolk into the
fimbriated portion, or funnel, of the oviduct. The walls of the ovarian
pocket are formed by the left abdominal air-sac, a part of the intestine, and
the mesentery. The dorsal portion is formed by the roof of the abdominal
cavity, and the ventral portion is formed by the dorsal wall of the air-sac.
The medial, the anterior, and the lateral limit of the pocket are formed by a
fusion of the wall of the air-sac to the mesentery and to the body wall.
Posteriorly, the wall consists of the transverse part of the small intestine and
the caudal portion of the left cæcum with their attached mesentery.

THE DUCTLESS GLANDS

These glands do not possess excretory ducts. They furnish materials
which are added to the blood or lymph as it passes through them. The
material from each gland is known as an internal secretion, or hormone.
Some of these secretions are powerful materials and influence profoundly
the body nutrition. The ductless glands are usually given as follows: the
spleen, the lymph glands, the pineal gland, the pituitary body, the thyroid
gland, the thymus gland, the adrenal glands, and the parathyroids. The
spleen, the pituitary, the pineal, and the lymph glands are described in other
sections.
The Thyroid Gland (Fig. 21, No. 16). Location.—The thyroid gland lies
on the ventral side of the carotis communis at a point where the carotis
communis touches the jugular vein, which is about the point of origin of the
vertebral artery.
Shape.—The thyroid gland is small, oval or somewhat roundish, and red
or rose-colored.
Structure.—The thyroid gland has a fibrous capsule, which sends into the
interior septa which divide it into acini. These acini are closed and contain a
fluid. The thyroid is a ductless gland. Short arteries from the carotis enter
this gland, and some large veins connect it with the jugular vein. The lymph
vessels which lie along the neck are closely connected with it and receive
twigs from the gland. The minute lymphatic capillary endings are found in
its septa and in its capsule. The acini are lined with a single or a double row
of cuboidal secreting cells. There are two kinds of cells, namely, secreting
and resting cells. The actively secreting cells secrete colloid.
The parathyroids consist of two small bodies attached to the lower pole
of the thyroid.

The Thymus Gland (Fig. 47, No. 10).—The thymus gland is an organ of
fetal and early baby chickhood. It soon undergoes retrogressive changes
into fat and connective tissue. It is of epithelial origin, being formed in fetal
life from the entodermal cells of the dorsal end of the throat fissure.
Location.—The thymus gland lies anterior to the thyroid, the latter lying
the deeper.
Shape.—The thyroid consists of two lobes, which are united by
connective tissue, and appears as a loop-like acinous gland lying along the
neck and near the region of the bronchi and the jugular veins with fibrous
extensions toward the head.
Structure.—The gland lobes are divided into lobules, which consist of a
cortical and a medullary portion. The cortex consists of nodules of compact
lymphatic tissue similar to those found in the lymph glands. These occupy
the chambers formed by the septa of connective tissue. In the medulla there
are a number of spherical, or oval bodies composed of concentrically
arranged epithelial cells. These are known as Hassall’s corpuscles, and
represent only the remains of the original glandular epithelium. They are
characteristic of the thymus gland. The thymus appears to be a type of
lymph organ. Lymph vessels are rare; a few blood-vessels on the upper side
form capillary nets.
The Adrenal Gland (Fig. 54, F). Location.—The adrenal gland, often
called the suprarenal capsule, lies just anterior to the front part of the
anterior lobe of the kidney, adjacent to the testicles in the male and to the
ovary in the female. It is loosely attached by connective tissue to the
posterior aorta and to the vena cava.
Shape.—It is yellowish-brown or reddish-pink in color, small, and of
irregular formation.
Structure.—The adrenal gland consists of a cortical and a medullary
portion, although these two parts are not distinctly marked. The cortical
portion has columns which extend deeply into the gland, and the medullary
portion sends columns into the cortical portion. Therefore, the two
substances, lying side by side, form a cord-like structure.
It is probable that the cortical portion is derived from the ingrowths of the
peritoneum, and the medullary cords from the sympathetic ganglion.

The cells are cylindrical or polygonal in shape, with an eccentric
substance between the columns. The cords, or columns, form between them,
elongated channels which extend into the interior of the gland and end as
blind or cæcal extremities. Large ganglionic nerve cells belonging to the
sympathetic system occur near the surface of the gland. The blood-vessels
are not well developed in the interior of the gland but are numerous and of
good size in the outer parts. Lymph vessels are also present.
Function.—The adrenals are ductless glands. They secrete an internal
secretion, or hormone, which influences the tonus of the blood-vessels. An
extract from these glands is called adrenalin.

THE RESPIRATORY APPARATUS (Figs. 50 and
61, A)

Owen says: “Notwithstanding the extent and activities of the respiratory
function in birds, the organs subservient thereto manifest more of a reptilian
than of the mammalian type of formation.”
By the action of the respiratory organs certain chemical and physical
changes take place in the blood. The chief of these consists in absorption of
oxygen from, and giving off carbon dioxide to, the atmospheric air, the
former changes being necessary for the elaboration of the fluid, the latter
for the elimination of a substance which, if retained, would prove injurious.
The organs of respiration are invariably adapted to the wants of the animal
and the medium in which it lives.
In the bird, which breathes through its nose, the organs of respiration are
nostrils, nasal chambers, pharynx, superior larynx, trachea, inferior larynx,
bronchi, bronchial tubes, lungs, and air-sacs.
The Nostrils and the Nasal Chambers.—The nostrils of the bird open
externally by two small elliptical openings, which pierce the upper
mandible. Within each nasal chamber (Fig. 26, A) are three turbinated
laminæ, or turbinated bones. The inferior one is a simple fold adhering to
the lower and anterior part of the nasal septum. The middle turbinated bone
is the largest. It is of infundibular form, and adheres by its base to the
septum and externally to the side wall of the nose. It is convoluted with two
and a half turns. The superior bone, of bell shape, adheres superiorly to the
frontal bone. The internal turbinated bone extends toward the orbit; the
external terminates in a cul-de-sac behind the middle turbinal (Fig. 26, No.
A, 1 and 2, and G).

The nostrils are separated by a partition which is partly bony and partly
cartilaginous. The posterior nares is represented by a long slit in the hard
palate.
The Pharynx and the Superior Larynx.—A transverse row of horny,
filiform papillæ marks the anterior border of the pharynx, where in other
animals the soft palate, or velum, is located. (For further description of the
pharynx see special chapter.)
The supero-posterior border of the larynx, at the juncture of the larynx
and the esophageal margin, is marked by a second transverse row of horny,
filiform papillæ, which point backward. There is no epiglottis. The superior
part of the larynx is pierced by an oval, slit-like opening, the glottis, which
is provided with two lips. These when brought together, tightly close the
glottis so that nothing can fall through into the larynx in the act of
deglutition. The margin, or rim, of this opening is called the rami glottis.
The glottis is controlled by two pair of muscles.
The superior surface of the larynx is somewhat triangular with the apex
directed forward. A few delicate, filiform papillæ are upon its surface. The
bird has, as already indicated, two larynxes, the superior larynx located at
the upper end of the trachea, and the inferior larynx at the bifurcation of the
trachea. The inner surface of the superior larynx is smooth and does not
contain vocal cords; it is in these animals simply a passage for air. It is
joined to the trachea inferiorly by a ligament, the crico-trachealis, and lies
at the base of the tongue supported by two cornua of the os hyoideum.
The cartilages forming the principal support of the superior larynx,
consist of four pieces, as follows: one unequal ventral piece, two side
pieces, and one unequal dorsal piece. The cartilaginous, flat, ventral cricoid,
early in the bird’s life, often becomes bony. The side pieces are separated
from it, only exceptionally fusing with it. The dorsal cricoid piece also often
becomes bony. The two arytenoid cartilages, joined with the cricoid
superiorly, are three-sided, and are united to each other in a sharp angle.
They form the superior opening of the superior larynx.
The Trachea.—The trachea is cylindrical and varies in length in
different kinds of birds in accordance with the length of the neck. It consists
of from 90 to 120 cartilaginous rings, complete with the exception of the
two uppermost, which rings are held together by intercartilaginous
ligaments. The tracheal rings are constructed of hyaline cartilage and the

ligaments of fibrous tissue. It is lined with a mucous membrane covered by
columnar epithelium. The trachea is a passage for air alone and terminates
in the inferior larynx.
The Inferior Larynx.—The inferior larynx, called the true larynx
because it is the organ of voice, is located at the inferior end of the trachea
and the superior ends of the bronchi. By some anatomists this organ has
been called the larynx broncho-trachealis. The larynx is flattened laterally
in fowls. It contains two membranous folds, which in the production of
sound are caused to vibrate. These folds are half-moon shaped elastic
structures, located in the bony, arrowlike way, intero-inferiorly. These
structures are called the membrana tympana interna. In the duck this
inferior larynx is represented by a drum-like cartilaginous and bony
structure, called the bulla tympaniformis. This bulla is a resonant apparatus
which serves to strengthen the voice.
In song birds there is a double glottis, usually produced by a bony bar,
called the pessulus, or os transversale, which traverses the lower end of the
trachea from front to rear. It supports a thin membrane which ascends into
the tracheal area, and, terminating there by a free concave margin, is called
the membrana semi-lunaris. This is most developed in singing birds, and
being vibratile, forms an important part of their trilling vocal apparatus. The
air passes on each side of the membrana semi-lunaris and its sustaining
bone to and from the bronchi and lungs.
The last ring of the trachea usually expands as it descends, with its fore
and posterior parts produced, and the lower lateral borders concave; the
extremities of the pessulus, butts against the angle thus formed and expands
to be attached, also with the fore and posterior terminations of the first half
ring of the bronchus, strengthening and clamping together the upper part of
the vocal framework. The second bronchial half ring is flattened and curved
with the convexity outward, like the first, but is more movable. The third
half ring is less curved and further separated from the second, to the
extremities of which its own are connected by a ligament, and, for the
intervening extent, by a membrane; its inner surface supports the fibrous
cord, or fold, which forms the outer lip of the glottis of that side; it is
capable of rotary movements on its axis, and is an important agent in the
modulation of the voice. All these parts just described are bony.

The Bronchi and the Lungs.—The bronchi, two in number, are
provided with only incomplete cartilaginous rings. They enter the inferior
face of the lungs, toward their anterior and middle thirds and break up into
primary bronchi, which give off at right angles, secondary bronchi, and
these latter in turn give off tertiary branches.

Fig. 61.—The lung.

A. The outer surface of one lung. Note
the flattened oval shape. It is not divided
into lobes. 1, The bronchus. 2, Primary
tubules showing openings leading from
the primary tubules to the secondary
tubules. 3, Openings of two of the large
tubes into the diaphragmatic and
abdominal air-sacs.

B. Sectioned surface of lung. 1,
Secondary tubules. 2, Tertiary tubules.
3, Interlacing capillaries and air cells.

C. 1, Cavity of tubule. 2, Its lining
membrane supporting blood-vessels
with large areolæ. 3, Perforations in the
membrane at the orifices of the lobular
passage. 4, Interlobular space containing
the terminal branches of the pulmonary
vessels supplying the capillary plexus,
5, to the meshes of which air gets access
by the lobular passage.

The lungs occupy only about one-seventh of the thoracic space. They are
long, flattened, and oval, extending along each side of the spine from the

second dorsal vertebra to the anterior end of the kidneys, and laterally to the
juncture of the vertebral with the sternal portions of the ribs. They present
two faces, a superior convex and an inferior concave; two borders, an
external and an internal; and two extremities, an anterior and a posterior
(Fig. 61). The convex surface is also called the dorsal, costal, or superior
face. It is moulded on the walls of the thorax and occupies a part of the
intercostal space, pushing the intercostal muscles outward. When the
surface of the lung is examined it is seen to be furrowed where the ribs
pressed during life. These furrows are as deep as the ribs are thick. The
sides of the lungs are covered with connective tissue which attaches them to
the costal walls.
The concave, or inferior, face also called the diaphragmatic or visceral
face is directed downward. The diaphragm separates it from the abdominal
viscera. The surface is covered by connective tissue which closely attaches
it to the diaphragm. It is perforated by the five tubules which bring the
posterior air-sac into communication with the lungs.
The borders of the lungs extend parallel to the long axis of the body. The
internal border is rectilinear, thick, and rounded. The external border is
convex, thin, and sharp.
The anterior extremity terminates in a sharp point which occupies a space
formed by the ribs externally and the inferior spines internally. The
posterior extremity is somewhat rounded and extends as far back as the
anterior border of the kidneys.
As soon as the bronchi enter the lungs they become broadened, the
cartilaginous rings disappear, and they continue as membranous channels
whose diameters gradually decrease, as they extend backward, to the point
where they terminate in the ostium caudale, at which point they are
surrounded by a cartilaginous ring. The ostium caudale brings the tubules
into communication with the ventral air-sacs.
Twelve air tubules have their origin from each common bronchus, or
trunk. Four are given off from the internal wall of the main bronchus by a
series of openings arranged in a row. Seven are given off from the external
wall by a second series similar to that of the first. The twelfth extends from
the inferior wall, and immediately takes a course downward and outward
and communicates with the posterior diaphragmatic air-sac. This may be
considered as the terminal branch of the trunk.

All of these secondary canals, except the last, pass toward the periphery
of the lung. They divide and subdivide at the periphery, covering it with
their ramifications. The canals extending from the inner wall are distributed
to the inferior face of the lung. Those extending from the outer wall are
distributed to the outer face of the lung. The first constitute the
diaphragmatic and the second the costal bronchial tubes.
The four diaphragmatic bronchial tubes are numbered in the order in
which they are given off. The first is carried forward horizontally, the
second transversely inward, the third obliquely inward and backward, and
the fourth directly backward. They have, by some anatomists, been called
the anterior, the internal, and the posterior diaphragmatic bronchial tubes.
There are two posterior diaphragmatic bronchial tubes; the larger called the
great posterior, and the smaller, which passes directly backward, the small
posterior.
The costal bronchial tubes, seven in number, are numbered from the
front backward in the order they are given off. Parallel at their origin, and
side by side, like pipes of an organ, they soon spread out in fan-shape like
the preceding. They extend from their central origin to the periphery. The
first extends obliquely upward and inward to the anterior extremity of the
lung. All branches from this bronchus extend from its anterior wall. The
first branches are inflected to reach the external border of the lung. The
succeeding branches are directed forward and the last forward and inward.
They all meet those from the anterior diaphragmatic bronchus, but do not
anastomose with them.
The second, the third, and the fourth costal bronchi extend in a transverse
manner and ramify on the inner border of the lung.
The fifth and the sixth are directed toward the posterior extremity of the
lung. The seventh, very small, reaches this extremity, where it disappears.
The first costal bronchus is the largest; those following it gradually
become smaller. At their points of origin they adhere closely to the ribs.
They are all imperforate, which is a distinguishing feature from those
occupying the opposite face.
The canaliculi or tertiary tubules given off by these secondary bronchial
tubes do not differ greatly in caliber in the various parts. They are given off
at right angles from the pulmonary wall of each bronchus, and extend
perpendicularly into the lung substance. Thus we find three kinds of

conduits, the primary, the secondary, and the peripheral, or tertiary. The first
are like the barbs of a feather on its shaft; and the second and
parenchymatous are implanted on the pulmonary walls of the first, like the
hairs of a brush on their common base. Thus instead of the branching of the
bronchi being dichrotomous, as in mammals, it is piniform.
The canaliculi, or finer tubules, communicate with one another. The inner
microscopic appearance of the canaliculi indicate that they are divided into
areola, which gives them a cellular aspect. These tertiary bronchi open on a
dense labyrinth of blood capillaries (Fig. 61, C). At this point the ciliated
epithelial cells give way to simple squamous epithelium.
Thus we find three kinds of bronchi, or their ramifications, as follows:
the primary, the secondary, and the tertiary.
The Air-sacs (Fig. 61, A).—The air-sacs are bladder-like structures
consisting of a delicate cellulo-serous membrane, an extension from the
bronchial tubes, in some places strengthened by an external envelope of
elastic fibrous tissue. Long thin blood-vessels are distributed in the
substance of these walls. They are branches from vessels of the general
circulation and not extensions from those of the lungs. No lymphatics have
been found in the air-sacs.

Fig. 61, A.—Diagram of air-sacs and their location. 1, The proximal end of the
humerus. 2, The proximal end of the right clavicle. 3, The cervical air cell. 4,
The right coracoid bone. 5, The anterior thoracic air cell. 6, The right side of the
sternum. 7, The right side of the liver. 8, The peritoneum. 9, The right abdominal
air cell. 10, The coccyx. 11, The proximal end of the right femur. 12, The right
supero-posterior air-sac. 13, The right infero-posterior air-sac. 14, The right lung.
15, The axillary extension of the air-sac. 16, The obturator foramen. 17. The
pelvis.

These sacs do not communicate with each other and normally they are
not fully inflated. In some locations they extend into the bones and are in
communication with the extensions of the bronchial tubes. In fact, by some
anatomists they have been called “bladder-like, extra-pulmonary expansions
of the bronchial tubes, free from cartilage.” The air-sacs make the bird’s
body lighter, thus making long-continued flight possible. They are best
developed in those birds which fly most. There are four pairs of cells and
one single cell from which all other expansions and extensions are made.
These sacs are as follows: a single anterior thoracic, and, in pairs, cervical,
anterior diaphragmatic, posterior diaphragmatic, and abdominal.
The Anterior Thoracic Air-sac.—The anterior thoracic air-sac is located
above the clavicles and the interclavicular space, in the cavity of the thorax.
It is related superiorly with the trachea and the esophagus; laterally with the

lungs and the cervical air-sacs; inferiorly with the sternum, the clavicle, and
the interclavicular aponeurosis; posteriorly with the heart and the anterior
diaphragmatic reservoir; and anteriorly with the integuments of the neck. It
contains the inferior larynx and the two primary bronchi, and large vascular
trunks from which are given off vessels supplying the neck and the wings.
Three prolongations, called subpectoral, subscapular, and middle, or
humeral, arise from the lateral walls of this air-sac. These prolongations
cross the walls of the thorax and pass around the articulation of the
shoulder.
The subpectoral prolongation extends from the thoracic reservoir by an
orifice situated behind the coracoid, and passes beneath the tendon of the
great pectoral muscle. When the pectoralis major contracts, this contraction
dilates the subjacent cell and draws into it a greater quantity of air.
The subscapular and the humeral prolongations communicate with the
thoracic air cell by a common opening situated behind the small adductor
muscle of the humerus. The subscapular prolongation, after leaving this
point, spreads under the scapular and the subscapular muscle, which it
separates from the ribs and corresponding intercostal muscles, and extends
in a longitudinal direction.
The humeral prolongation, smaller than the subscapular, occupies the
axilla, and is in shape triangular. It has from its summit into an infundibular
fossa, an extension which enters the canal of the humerus. The walls of this
cell form the lining of the air space in the humerus.
The thoracic air-sac thus possesses numerous membranous folds which
divide its cavity. The contiguous structures which it overlies, as the trachea,
the esophagus, the muscles of the inferior larynx, as well as the arteries and
veins, make its outer walls irregular. This orifice is dilated during
inspiration, by the contraction of the two first fasciculi of the diaphragm.
The Cervical Air-sacs.—The two cervical air-sacs are located just above
the thoracic air-sac at the inferior part of the neck and in front of the lungs.
They are cone-shaped with the base directed forward and the apex
backward. They are related superiorly with the cervical muscles, and
inferiorly with the thoracic air-sac from which they are separated by the
trachea, the esophagus, the pneumogastric nerve, and the jugular veins. The
walls touch each other internally, and form a median septum which includes
in its substance the two common carotid arteries. Externally they are related

to the origin of the cervical nerves, to each of which they contribute a small
sheath. They surround the vertebral artery, and are connected with the
subcutaneous muscles and the skin. The summits communicate with the
anterior diaphragmatic bronchus. Prolongations extend from their bases
which conduct the air into all the vertebræ of the neck and the back, into all
the vertebral ribs, and into the spinal canal. Parallel with and adjacent to the
vertebral arteries, and lodged in the canals excavated in the transverse
processes of the cervical vertebræ, are two cervical prolongations, one on
each side, which extend to the cranium from the base of the cervical
reservoirs. From their sides, at the last six cervical vertebræ, are six
extensions in the form of diverticuli, which, lying against each other, pass
from each side into the muscles of the neck. They are surrounded by a thin
fibrous envelope, a continuation of the mucous lining of the sac, and
apparently form a canal in the inferior part of this region. These
prolongations are better developed in palmipedes than in chickens. On the
internal side of these prolongations, one or more foramina penetrate the
vertebral segment, which allow the extensions of the prolongations into the
spinal canal. Chauveau states that “as the medullary tissue is replaced by air
in the bones of birds, so is the subarachnoid fluid replaced by air around the
spinal cord.”
The prolongations extending from the cervical air-sacs, having entered
the thorax, terminate by passing into the first dorsal vertebra. After
permeating every part of this vertebra, it escapes by a lateral opening and
forms a small sac located between the first two ribs, near the origin of the
first dorsal nerve. From this sac an extension is given off, which enters the
second vertebral segment at the antero-lateral part; from this point it passes
back, forming a new air-sac between the second and third ribs. It now
passes in the same manner into the third vertebra and extends through the
third intercostal sac, and so on till the last dorsal vertebra has been served.
At the same time that these sacs receive the air from the vertebræ preceding
them, and transmit it to those which follow, they communicate it to all the
vertebral ribs. The aerial currents which leave the cervical air-sacs do not
communicate with those of the cranium. Experiments show that the cranial
bones have apparently no communication with the respiratory apparatus.
The Anterior Diaphragmatic Air-sac.—The two anterior diaphragmatic
or supero-posterior air-sacs are related with the lungs anteriorly, and with
the abdominal viscera posteriorly. Anteriorly also is the thoracic air-sac,

posteriorly are the posterior diaphragmatic air-sacs, and laterally the ribs
and the intercostal muscles and internally is the esophagus. The lungs
communicate with these air-sacs through circular openings from the great
posterior diaphragmatic bronchus and frequently by a second opening from
this same tube. These are the only sacs which receive air from the lungs
through two openings.
The Posterior Diaphragmatic Air-sac.—The two posterior
diaphragmatic, or infero-posterior air-sacs are oval in shape and located
between the thoracic and the abdominal cavity. They are related anteriorly
with the anterior diaphragmatic air-sacs. These two sacs form a vertical
transverse partition. The posterior diaphragmatic air-sacs are related
posteriorly with the abdominal air-sacs from which they are separated by
the diaphragm. They are related below with the lateral parts of the sternum
and the sternal ribs, and externally with the ribs and the intercostal muscles.
These air-sacs communicate with the lungs through openings located in the
middle part of the external border of the lung, into the extremity of
voluminous bronchial tubes which follow the direction of the largest air
tubes.
The Abdominal Air-sacs.—The two abdominal air-sacs located on each
side of the abdominal cavity, when inflated with air, form enormous
bladder-like structures. They are related laterally with the abdominal wall
and internally with the abdominal viscera. The anterior extremities are in
communication with the mesobronchi and are somewhat inflected to pass
under the fibrous arches extending from the spine to the pelvis. Anteriorly
these sacs adjoin the diaphragm, the testes in the male, and ovary in the
female, and to the parietes of the abdomen and those of the pelvis. Below
and in front, they rest on a fibrous septum, which in all birds divides the
abdominal cavity into two smaller cavities: one anterior, representing the
abdomen and containing the liver; the other posterior, representing the
pelvis and containing the gizzard and the intestines. The anterior portion
overlies the posterior part of the lobes of the liver, the proventriculus, the
spleen, and the gizzard. The kidneys are located above these air-sacs.
Dorsal to the sacs is also a part of the intestines and in the female the
oviduct. The abdominal air-sacs are attached by a ligament-like structure in
their medial, their anterior, and their lateral margin. The posterior, the
dorsal, and the ventral margin are free. Mesially this attachment is to the
mesentery, connecting the left cæcum to the dorsal margin of the gizzard,

and also to the mesentery of the proventriculus. The anterior attachment is
to the body wall and extends in front of the end of the ovary and the adrenal
glands. At the antero-lateral part of the body cavity the attachment extends
in a widening band along the lateral side of the ovary and of the oviduct, as
far back as the caudal margin of the sac. The lateral attachment is related to
the kidney, the dorsal ligament of the oviduct, and the abdominal wall.
Each of these abdominal sacs has three extensions: one suprarenal and
two femoral.
The suprarenal extension leaves the principal sac at the postero-external
part of the kidney, extends upward, and forward, and expands over the
surface of the kidney. At the internal border of the kidney, this prolongation
extends between the transverse processes of the sacral vertebræ, reaches a
height of the first dorsal vertebra, forms a triangular canal located above the
sacrum in the sacral channel, and is separated from its fellow by a series of
corresponding spinous processes.
The two femoral extensions, an anterior, small, and a posterior, large,
extend from the abdominal air-sac at the cotyloid cavity, leave the pelvis
through the bony passage occupied by the crural vessels, extend around the
coxo-femoral articulation, and terminate in a blind extremity. In some birds,
particularly in birds of prey and ostriches, there are prolongations extending
into the femur, entering through a foramen at the anterior part of the great
trochanter.
Summary of Bones Supplied by Each Air-sac.—The thoracic air-sac
communicates on each side of the thorax with twelve bones, including the
four sternal ribs. It supplies air to the clavicles, which are perforated at both
their extremities, and to the coracoids, which are perforated just below their
scapular extremity. The sternum is supplied through two series of openings,
the middle ones that conduct air into the sternal ridge and the lateral ones,
eight in number and very small, correspond to the intercostal spaces. The
sternal ribs are penetrated by small foramina at their inferior extremities.
From the subscapular extension the scapulæ receive air through one or two
foramina at their anterior extremity. The humeral prolongation supplies the
humerus through a foramen located at the upper edge of the humeral fossa,
at the infero-internal part of the articular head.
The cervical air-sac furnishes air to all the cervical vertebræ, to all the
dorsal vertebræ, and to all the vertebral ribs. The anterior parts of the

vertebræ of the neck are supplied with air through the passage
accommodating the vertebral artery. The posterior parts of the vertebræ are
supplied by extensions from the interspinal canal. The first extensions
obtain entrance to the anterior segments by one or more openings of the
inner wall of the intertransverse canals; the median extensions penetrate the
posterior segments by two openings, a right and a left, situated on the inner
wall of those segments. The first dorsal vertebra is supplied with air in the
same manner, by the middle and the lateral canals of the neck. This air, after
passing through the first vertebra, leaves by a lateral exit to enter a small
air-sac. From this it passes into the superior part of the second vertebra,
escapes from this through its lower portion, to be received into a lateral sac,
and so on to the last dorsal vertebra. These sacs also supply the vertebral
ribs with air, which enters them by very small openings located on their
spinal extremities.
The diaphragmatic air-sacs do not have communications with the bones.
The abdominal air-sacs communicate with the sacrum, the coccygeal
vertebræ, the iliac bones, and the femurs. The air passing through the
sacrum, the coccyx, and the ilium comes directly from the suprarenal
extensions; the air which fills the femoral cavity comes from the femoral
extensions.
In some birds these air spaces are more greatly developed than in others.
The bones that are always aerated in all birds are the cervical and the dorsal
vertebræ, the sternum, and the humeri. Those aerated in some kinds only
are the furculum, the scapulæ, the vertebral and the sternal ribs, the sacrum,
the coccyx, and the femurs. Those that are never aerated are the bones of
the forearm, the hand, the leg, and the foot.
The service of air to the bones in most parts of the body by the air-sacs,
as just shown, is in special cases otherwise rendered. The Eustachian tubes
furnish air to the bones of the cranium and to the upper jaw; while the lower
jaw receives air from the pneumatic foramen situated upon each ramus
behind the tympanic articulation, and from an air cell which surrounds the
joint.
The cavities of the embryonic bones, which afterward become
pneumatic, are filled with marrow. Selenka states that the invasion of the
bones by the air is a late development, and that in the humerus this invasion
occurs after the twenty-second day in the life of the chick.

Hunter and Compar, who have made extensive researches, consider the
function of the air-sacs as threefold.
First, the air-sacs are subsidiary respiratory organs, which aid in ridding
the blood of waste products and in taking in oxygen.
Second, they aid mechanically the actions of respiration in birds. During
the act of inspiration the sternum is depressed, the angle between the
vertebral and the sternal ribs is made less acute, and the thoracic cavity
proportionately enlarged; the air then rushes into the lungs and into the
thoracic receptacles, while those of the abdomen become flaccid. When the
sternum is raised, or approximated toward the spine, part of the air is
expelled from the lungs and the thoracic air-sac through the trachea, and
part is driven into the abdominal receptacles, which are thus alternately
enlarged and diminished with the expansion and the contraction of the
thorax. Hence the lungs, notwithstanding their fixed condition, are subject
to due compression through the medium of the contiguous air receptacles,
and are affected equally and regularly by every motion of the sternum and
of the ribs.
Third, they reduce decidedly the specific gravity of the whole body. This
must necessarily follow from the large spaces filled with air as well as from
the absence in the bones of marrow and other fluids. The air-sacs by their
position also render equilibrium more stable.

ANGIOLOGY

The Circulatory Apparatus.—The circulatory apparatus consists of two tubular systems: the blood vascular
system and the lymphatic system.
The blood vascular system consists of the heart, the arteries, the veins, and the capillaries.
The heart is the central, propelling organ. The arteries form a series of efferent tubules, which, by branching,
constantly increase in number and decrease in caliber, and which serve to carry the blood from the heart to the
tissues. The capillaries are extensions from these latter tubules into which the arteries empty, and through the walls
of which the interchange of elements between the blood and the other tissues takes place. The veins form a system
of converging tubules which receive the blood from the capillaries, decrease in number and increase in size as they
approach the heart, and return the blood to that organ.
The lymphatic system consists of capillaries and veins alone. As in the blood system, the lymph capillaries
collect the effete material and pour it into the lymph veins, and these in turn, carry it to the large blood veins
adjacent to the heart.
Both these systems have one and the same continuous lining, which consists of a single layer of endothelial
cells. In the heart this lining is called the endocardium, and in the vessels, the endothelium. It forms a perfectly
smooth surface.

THE HEART (Fig. 21, No. 7)

The heart of the domestic fowl is located in the median line of the thoracic cavity. It is more anterior and mesial
than in mammals. Its axis is parallel with the axis of the trunk. The lungs being confined to the dorsal part of the
trunk, the lower part of the heart is not surrounded by them, but extends backward, the apex resting in the anterior
part of the anterior median fissure of the liver.
The heart has the form of an acute cone (Fig. 50, No. 1), the apex of which is bluntly rounded.
The heart is surrounded by a sero-fibrous sac, the pericardium. This sac adheres to the cervical air reservoirs
anteriorly and to the diaphragmatic septum posteriorly. It is composed of two membranous layers: the parietal,
external, dense, and fibrous; and the visceral, internal, and serous. The pericardial sac has no direct attachment to
the heart, except at the upper extremity where it surrounds the large vessels emerging from it. The serous layer is
reflected over the outer portion of the heart, where it is called the epicardium. The function of the pericardium is to
prevent friction during the beating of the heart. It contains a small amount of serous fluid for perfect lubrication.
This fluid is called the liquor pericardii.
Internally the heart has four cavities: two auricles and two ventricles. The right ventricle is more crescent-
shaped than in solipedes, and in a manner envelops the left ventricle in front and to the right, though it does not
reach the point of the heart. The right auricle is larger than the left. The auriculo-ventricular valve is not tricuspid
as in mammals. This valve instead of being formed as usual by a membranous curtain, with margins retained by
cords fixed to the walls of the ventricles, is composed of a wide muscular leaf, which appears to be a portion of the
inner wall of the ventricle detached from the interventricular septum. This septum is convex; and the auriculo-
ventricular orifice is an oblique slit situated between it and the muscular valve in question; so that, when the heart
wall contracts at the systole, the valve is applied against this septum and closes the passage. The bicuspid, or
auriculo-ventricular valve of the left side usually has two segments, though occasionally there may be three. The
fossa ovalis is a depression behind the posterior semi-lunar valve in the septum of the heart. The membranous
septum closing the foramen ovale is complete and strong but thin and transparent. The right auricle receives the
blood from the two venæ cavæ coming from the anterior extremity, and from the posterior vena cava. These empty
into a sinus. The left auricle has two vessels, the pulmonary veins which bring blood to it from the lungs.

Structure of the Heart.—The heart is lined by a serous membrane, the endocardium, which is a continuation of
the endothelium of the blood-vessels. There are a few muscular pillars in the inner wall, called the columnæ carnæ.
To give the heart its pumping power, it is made up of contractile tissue, a specialized kind of muscle called heart
muscle. It is involuntary-striated and occupies an intermediate position, both morphologically and embryologically,
between smooth involuntary muscle and striated voluntary muscle (Fig. 74, No. 4). It, like striated voluntary
muscle, is both transversely and longitudinally striated. Heart muscle cells are short, thick cylinders, which are
joined end to end to form long fibers. By means of lateral branches the cells of one fiber anastomoses with cells of
adjacent fibers. Each cell of heart muscle contains one centrally located nucleus. There is no distinct sarcolemma,
but the sarcoplasm is more dense near the surface of the cell, which gives it the appearance of an enveloping cell
wall. There is a zone free from fibrillæ around the nucleus. The longitudinal fibrillæ, which make up the cell, are
held together by a cement-like substance.
The main mass of the heart wall, called myocardium, consists of the specialized muscular tissue just described.
The myocardium differs in thickness in different parts of the heart wall. It is thickest in the left ventricle and
thinnest in the auricles. The left ventricle forces the blood through the systemic circulation and hence must be
thicker to give it more power than is needed for the right ventricle, which forces the blood only through the lungs.
The auricles are thinnest of all; for they receive the blood and pass it only to the chambers below. The auricular
appendages at the base of the heart in fowls are not so well marked as in mammals. The auricular muscles consist
of an outer coat common to both auricles, the fibers of which are transverse and of an inner coat, independent for
each auricle, the fibers of which are longitudinal. Between the two coats, occur bundles of muscle the fibers of
which run in various directions. The disposition of the muscle tissue of the ventricles is much more complicated. It
is composed of several layers of fibers intricately interwoven.
The endocardium, covering the inner surface of the myocardium, forms a serous lining of all the chambers of
the heart. At the arterial and venous openings it is continuous with and similar in structure to the intima of the
vessels. The endocardium consists of two layers, an external layer closely attached to the myocardium and

consisting of mixed fibers, including those of elastic tissue and smooth muscle cells; and an inner, single layer of
endothelial cells, spoken of above.
The heart is supplied with nutrient blood by the two coronary arteries, which are given off from the common
aorta just above the semi-lunar valves.
A right, or anterior, and a left, or posterior, coronary from their point of origin, turn in a ventral direction
between the root of the aorta and the pulmonary artery, the right going to the right coronary groove and the left to
the left coronary groove in the crown furrow. From here they send branches into the heart. The anterior, right,
coronary, or coronaria dextra, the larger, is given off from the inferior wall of the aorta. It divides into a ramus
superficialis and a ramus profundus. The ramus superficialis enters the crown furrow and divides into two or three
branches on the right heart wall. These branches extend to the apex of the heart. Twigs from this artery along its
course extend into the muscular wall reaching the posterior of the coronary groove where they anastomose with
those of the left coronary, the ramus profundus, and with other branches from the same artery. The ramus
profundus, larger than the preceding, gives off fine branches into the walls of the aorta and of the pulmonary
artery, then enters from behind into the right wall of the septum ventriculorum, extends into the apex of the heart,
and supplies the septum, or right inner chamber wall with the last branch, this breaking through the posterior wall
of the auricular appendage.
The posterior, left coronary, or coronaria sinistra, originates from the dorsal wall of the aorta, proceeds as one
branch on the upper surface of the left auricular appendix, and then extends between the left appendix and the
pulmonary artery to the ventral surface of the heart. On the left side it supplies the wall of the pulmonary artery
and gives off a ramus profundus. It sometimes divides into two parts and supplies the ventral wall of the right
chamber and then extends to the left wall of the septum medium. The rest of the coronaria sinistra enters into the
left crown furrow as the ramus superficialis, which provides the left and dorsal upper surface of the left chamber to
the apex. From this furrow it extends into the left chamber and the left appendage, and finally fuses with the ramus
superficialis of the coronaria dextra.

THE BLOOD-VESSELS

The blood-vessels consist of arteries, veins and capillaries.
The Structure of the Capillaries and Arteries.—The capillaries are minute vessels which connect the
arterioles, or terminal arteries, with the venules, or terminal veins. They are only from 6 to 14 microns in diameter.
Their walls consist of a single layer of endothelial cells, which are somewhat elongated in the long axis of the
vessels. Their edges are serrated, and are united by a small amount of intercellular cement-like substance.
Capillaries branch without diminution in caliber, and these branches anastomose to form capillary networks, the
meshes of which differ in size and shape in different tissues and organs. The largest meshed networks occur in the
serous membranes and in the muscles; and the smallest occur in the glands, such as the liver.
The walls of the arteries are thick and stand open when empty, owing to the elastic tissue contained in their
walls, while the walls of the veins collapse when empty, owing to their containing a smaller amount of elastic
tissue. The arterial wall is provided with three coats: tunica intima, or inner coat; tunica media, or median coat;
and tunica adventitia, or outer coat.
The tunica intima consists of a single layer of endothelial cells, continuous with and similar to that forming the
walls of the capillaries. In passing from the capillaries to the arterioles, there is first a thin coat, or sheath-like
layer, of connective tissue around the outside of the endothelial tubes. Further along, isolated smooth muscle cells
arranged in a circular manner occur between the endothelial layer and the layer of connective tissue, this structure
forming vessels called precapillary arteries. Further along still, the muscle cells form a complete layer; in this
section the vessels are called arterioles and are made up of three coats: the inner endothelial, the middle muscular,
and the outer fibrous.
In arteries of medium size the intima consists of the endothelial layer, a layer of delicate white and elastic fibers,
connective-tissue cells, and the membrana elastica interna, or an outer layer, the elastic layer, of the intima.
The media consists of a thick coat of circularly arranged smooth muscle cells, its thickness depending largely
upon the size of the vessels. There is also a small amount of fibrillary connective tissue, which supports the muscle
cells. Elastic tissue is present in the media, the amount depending on the size of the vessel, the larger the vessel the
more elastic tissue there is present. In the large arteries coarse elastic fibers intermingle with the finer ones. When
much elastic tissue is present the muscle cells are separated into more or less well-defined groups.
The adventitia is composed of loose connective tissue with some elastic fibers. A few smooth muscle cells are
present, which, as are also the elastic fibers, are arranged longitudinally. The adventitia, blending with the
connective tissue surrounding the arteries, serves to anchor the vessels to the surrounding structure.
Structure of the Veins.—In many respects the walls of the veins resemble those of the arteries. The same three
coats exist and the same elements enter into their structure. The transition from capillary to small veins, and from
those to larger veins, is similar to the transition from the arteries to capillaries, in inverse order. The walls are not
so thick as those of arteries. The elastic tissue is much less in quantity and in smaller veins disappears. There is not
a clear line of demarcation between the intima and the media.
The veins of birds differ from those of mammals in that they have fewer valves. The valves are also less perfect,
and often permit a backward flow of blood.
The walls of the arteries and of the veins are supplied with nutrient blood-vessels. These are called the vasa
vasorum, or blood-vessels of the blood-vessel wall. They are mostly in the adventitia. They may arise from the
vessel to which they are distributed or take origin from an adjacent vessel. These small arteries supplying the
vessel coat after terminating into capillaries form small veins through which the blood, from the structure of the
vessel wall, is returned.
The walls of the blood-vessels are supplied with both medullated and non-medullated nerves. The non-
medullated nerve fibers are axones of the sympathetic neurones and control the caliber of the vessels. These fibers
are called the vasomotor nerves. They form plexuses in the adventitia, from which are given off branches which
penetrate the media and terminate on the muscle cells. The medullated nerves are the axones of the spinal nerves.
The larger fibers are found in the connective tissue outside the adventitia and give off branches to the media where
they divide repeatedly, lose their sheath, and terminate in the media and at times in the intima.

The Arterial Trunks

The common aorta is short; it originates from the left ventricle (Fig. 61B, No. K, 14), and is guarded by three
semi-lunar valves. The aorta breaks through the pericardium just to the right of the pulmonary arteries in a ventral
direction; it then turns upward dorsally and to the right of the inferior bodies of the vertebræ. It is then directed
anteriorly, and dorsally to the right bronchus, between the right bronchus and the right lung. The right and the left
coronaries are given off from the common aorta; they have been discussed. There is next given off the left brachio-
cephalic or brachio-cephalic sinister artery (Fig. 61B, No. K, 10), which is just above the border of the base of the
heart. This artery passes upward and slightly forward, over the center of the inferior larynx. Just beyond this point
the subclavian artery is given off; this artery later becomes the axillary and the axillary the brachial artery. Then
there is given off the anterior and the posterior thoracic arteries; and finally, the pectoral, which supply the
pectoralis muscles and later terminate in the carotid, the vertebral, and the cervical arteries. The carotid artery
gives off an esophageal artery. The other arterial trunk given off from the common aorta is the right brachio-
cephalic or brachio-cephalic dexter (Fig. 61B, No. K, 18). The right brachio-cephalic artery gives off the
subclavian, which continues as the axillary, and continues as the brachial artery. There is given off the anterior and
the posterior thoracic, the right carotid (Fig. 61B, No. K, 11), the vertebral, and the dorsal. The last continues as the
cervical.

Fig. 61B.

K. The arterial trunks. 1, The middle sacral artery. 2, The hypogastric
artery. 3, The posterior mesenteric artery. 4, The ischiadic artery. 5, The
femoral artery. 6, The renal artery. 7, The left pectoral artery or thoracico
caudalis. 8, The left axillary artery. 9, The left carotid artery. 10, The left
brachio-cephalic artery. 11, The right carotid artery. 12, The right brachial
artery. 13, The right pectoral artery. 14, The common carotid artery. 15,
The posterior aorta. 16, The celiac axis. 17, The anterior mesenteric artery.
18, The right brachio-cephalic artery. 19, The auricular portion of the heart.
20, The ventricular portion of same. 21, Sterno-clavicular artery. 22, Anterior
thoracic.

L. The venous trunks. 1, The caudal vein. 2, The coccygeo-mesenteric vein. 3, The posterior mesenteric vein. 4, The
anterior mesenteric vein. 5, The gastro-duodenal vein. 6, The portal vein. 7, The hepatic vein. 8, The left anterior vena
cava. 9, The left pectoral vein. 10, The left brachial vein. 11, The left jugular vein. 12, The right jugular vein. 13, The right
brachial vein. 14, The right pectoral vein. 15, The right anterior vena cava. 16, The posterior vena cava. 17, The common
iliac vein. 18, The femoral vein. 19, The renal vein. 20, The internal iliac vein. 21, The hypogastric vein. 22, The auricular
portion of the heart. 23, The ventricular portion of same.

The pulmonary arterial trunk is given off from the conus arteriosus of the right ventricle. It is guarded at its
origin by three semi-lunar valves similar to those of the aorta. The trunk divides into two pulmonary arteries,
which are short, one called the pulmonalis dexter and the other the pulmonalis sinister. The former goes to the right
and the latter to the left lung. Each branch penetrates the lung near the bronchus. These arteries divide, or branch,

similarly to the bronchi. Following the branchings of the bronchi, they finally terminate into the lung capillaries,
forming networks on the bronchi and the air-tube terminals.

BRANCHES OF THE BRACHIO-CEPHALIC ARTERY

( Thyroidea

( ( Cervicalis inferior

( Vertebralis ( Vertebralis anterior

( ( Vertebralis posterior

( ( Arteria cervicalis ascendens

( Bronchiales

( Truncus ( Inferior esophageal

( caroticus ( Subcutaneous colli

( ( ( Carotis cerebralis

( ( Carotis ( Cervicalis superior

( ( communis ( Occipitalis

( ( ( Carotis externa

( ( Spinalis anterior ( Basilaris ( Cerebelli inferior

Brachio-cephalic (

( ( Clavicularis

( ( Sterno-clavicularis ( Sternalis

( ( ( Acromialis

( (

( ( ( Subscapularis

( ( ( ( Ulnaris

( Subclavia ( Axillaris ( Brachialis ( Brachialis profunda

( ( ( Radialis

( ( Humeralis ( Circumflex humeralis

( ( ( anterior

(

( ( Thoracica externa

( Thoracalis ( ( Arteria thoracica

( Thoracica inferior ( longa

(

( Mammaria interna

( Circumflex humeralis posterior

Brachialis profunda ( Collateral ulnaris

( Collateral radialis

The cord-like remnant of the ductus botalli, or embryonal connection between the lung arterial trunk and the
anterior aorta, has been observed but is rare in grown birds.
The arteries, the veins, and the lymphatic vessels of birds anastomose far more frequently than those of
mammals.

BRANCHES OF THE ARTERIA CAROTIS CEREBRALIS INTERNA

( Occipitalis ( Occipitalis sublimis

( ( Occipitalis profunda ( Meningea

( ( Temporalis

( ( ( Rete t

( Ophthalmica ( Recurrent ophthalmicum ( Rete ethmoidalis

( externa ( Ethmoidali

( ( Plexus palpebralis

( ( Plexus alveolaris inferior

( ( Plexus muscularis

Carotis cerebralis ( Plexus temporalis ( Plexus lacrimalis

( ( Ramus ciliaris posticus

( ( Meningea media

(

( ( Sphenoidea (

( ( Spheno-maxillaris ( Ethmoidalis ( extern

( ( ( Ophthalmica ( (

( ( ( interna (

( Cerebralis ( (

( Ramus ( Sylviæ

( anterior ( Cerebralis profunda ( Choroid plexus

( Arteria centralis retinæ

( Ramus posterior

BRANCHES OF THE ARTERIA CAROTIS EXTERNA

( Hyoidea

Carotis externa ( Laryngea superior

( Facialis

( Lingualis

BRANCHES OF THE ARTERIA CAROTIS FACIALIS

( Auricularis

Facialis ( Facialis interna ( Alveolaris inferior ( Mentalis

( Maxillaris interna

( Facialis externa

Branches of the Carotid Trunk

The carotis communis artery springs from the carotid trunk of the brachio-cephalic. It is directed horizontally,
ascending to the ventral side of the neck. It then extends downward to the inferior median neck region. Just after
leaving its origin it gives off several small branches to the bronchi and to the esophagus, and extends toward the
head. The carotid lies on the thyroid gland and at this point touches the jugular vein (Fig. 21). At this point the
thyroid arteries are given off from the carotid trunk. The thyroid gland also receives blood from the bronchialis
artery.
Dorsalward and near the thyroid gland the carotid artery gives off a branch (the bronchialis) which accompanies
the recurrent laryngeal nerve, along the inferior larynx and the bronchi, and supplies the lung substance and that
part of the esophagus in this region.
The vertebral artery is given off from the carotid trunk, dorsalward to the thyroid gland, and on the left side.
The right vertebral artery may be given off from the brachialis dextra or right brachialis.
The inferior esophageal artery is given off from the ventral side of the carotid, supplies the esophagus, extends
then to the skin of the neck and to the trachea, is directed anteriorly toward the head and anastomoses with the
vertebral artery. This artery accompanies the vagus nerve and forms a collateral artery to the carotid and the
vertebral artery.
The subcutaneous colli springs from the carotid artery near the thyroid gland and communicates with the
inferior cervical artery, which, in turn springs from the vertebral artery.

The Common Carotid.—Near the last cervical vertebra the two carotid arteries occupy the same channel, to
which they are attached by fascia, and, lying close to the inferior surface of the bodies of the cervical vertebræ, are
covered by the colli muscles. Near the third or the fourth cervical vertebra, the two carotid arteries separate. Near
the atlas each carotid divides into the carotis cerebralis and carotis externa. Near this division the superior
cervical artery branches off. This latter artery extends down the neck in company with the pneumogastric nerve
and the jugular vein, supplies the skin and the neck muscles, and anastomoses with the inferior cervical artery and
the subcutaneous colli artery.
The occipital artery originates either from the carotis communis or sometimes from the superior cervical.

Branches of the Carotis Cerebralis

The branches of the carotis cerebralis are as follows:
1. The occipitalis (Fig. 72, No. 18), which in turn gives off, first, the occipitalis sublimis. The occipitalis
sublimis supplies the outer and the middle portion of the digastricus and the posterior mylo-hyoideus muscle. It
also gives off, second, the occipitalis profunda which supplies the inner portion of the digastricus muscle and
becomes the meningeal artery, which passes through the foramen vagi, entering the brain cavity, where it supplies
the coverings of the brain as far as the sella turcica. Superficial branches of this artery are distributed to the
muscles in the region of the atlas and anastomose with the vertebral artery.
2. The ophthalmica externa, which passes below the articulation of the quadrate bone, around the tympanic
cavity, enters the canalis caroticus, and passes into the cranial cavity. The ramus occipitalis, passing out of the
same foramen, again enters the diploë of the cranium; then after passing dorsally over the upper outer semicircular
canal of the ear, passes backward through the occipital bone.
The ophthalmica externa (Fig. 72, No. 9) forms a main trunk and gives off two branches: the temporal artery
and the recurrent ophthalmic. The recurrent ophthalmic gives off the rete temporalis, rete ethmoidalis, a branch to
the orbital gland, and finally anastomoses with its own branches and with those of the internal ophthalmic at the
olfactory foramen and aids in forming the ethmoidal artery. These arteries supply blood by giving off branches to

the muscles of the eye, sclerotic coat, iris, choroid coat, and the ciliary bodies. It gives off another branch to
Harder’s gland, and finally anastomoses with the ethmoidalis.
3. The plexus temporalis, rete mirabile ophthalmicum, or wonderful network (Fig. 72, No. 8), is formed
between the second and the third trunk of the trigeminus nerve and the rete ophthalmicum.
Inferior to this is the alveolar plexus, which plexus accompanies the third branch of the trigeminus into the
lower jaw. Two main branches form this plexus, one coming from the carotis facialis, which anastomoses with the
alveolar artery.
The palpebral plexus lies between the trunks of the trigeminus, and supplies mainly the lower eyelid.
The plexus muscularis extends to the fifth portion of the temporal muscle.
The plexus lacrimalis forms on the posterior orbital wall on the ramus ethmoidalis and supplies the lacrimal
gland and the upper eyelid. It anastomoses with branches from the facial artery.
The ramus ciliaris posticus supplies the inferior rectus and the external rectus muscle of the eyeball. It
anastomoses with the ophthalmica externa.
The median meningeal artery passes through the foramen occupied by the second branch of the trigeminal
nerve. Passing into the cranial cavity, it supplies the dura mater. Before passing into this foramen, small branches
are given off, which supply the skin and the temporal muscle; and some branches anastomose with the superior
cervical and the ethmoidal arteries.

4. The Cerebral Artery.—Each cerebral artery enters the cranial cavity through the canalis caroticus located in
the sphenoid bone, passes forward medially from the cochlea, dorsally from the Eustachian tube, and passes
through a small canal which opens on the inner surface of the sella turcica. Originating in this foramen, the
sphenoid artery divides into two branches which anastomose with the pterygoidean and the pterygo-pharyngeal
artery and which supply the upper jaw and the throat regions.
The spheno-maxillaris artery supplies the gums.
The right and the left cerebral arteries unite at the sella turcica. After this union they divide again immediately
and pass to the base of the brain, where they give off twigs to the optic nerve, to the optic chiasm, and where also
is given off the arteria retinæ centralis. Passing posteriorly each cerebral artery gives off the ramus posterior, and
then passes to the side of the cerebellum.
The basilar artery, a continuation of the anterior spinal artery, is located ventrally and mesially to the
cerebellum. Laterally and inferiorly the basilar artery gives off the inferior cerebellar artery.
The ramus anterior is given off from the cerebralis artery and continues as the internal ophthalmic artery. The
ramus anterior also gives off the sylvian artery, which supplies the sides of the cerebrum and the middle brain. In
the fissure between the hemispheres and the optic thalamus is located the arteria cerebri profunda. This artery
passes along the median surface of the cerebrum and in its course supplies the adjacent parts. It enters into the
formation of the choroid plexus of the lateral ventricle.
The internal ophthalmic artery extends out of the cranial cavity, through the optic foramen, into the orbital
cavity. It passes upward along the interorbital wall and supplies the optic nerve, the trigeminus nerve trunk, and the
eye muscles, and dorsally anastomoses near the olfactory nerve with the rete ethmoidale and the external
ophthalmic artery, and continues as the ethmoidal artery.
The ethmoidal artery supplies the supra-orbital gland and the gland of Harder. It gives off twigs to the rete
ophthalmicum and other branches to the skin of the frontal region, where it anastomoses with branches of the
external facial artery. These branches in the frontal region are rather large. Large branches are given off to the
comb.
The arteria ethmoidalis externa originates in the nasal cavity from a division of the ethmoidal artery.
The external ethmoidal artery passes below the lacrimal bone, extends forward, supplies the walls of the nasal
cavity, and finally sends a branch anteriorly into the upper median portion of the jaw bone, and other branches to
the septum nasi and other parts of the nasal cavity.
There are frequent anastomoses between the ethmoidalis interna, the facialis, and the spheno-maxillary artery.
The internal ethmoidal artery supplies principally the posterior turbinated bones and septum nasi.

Branches of the External Carotid Artery

Branches from the external carotid and the facial artery supply the tongue and its muscles, the larynx, the lower
jaw bone, the gums, and the upper lateral facial region.
The external carotid (Fig. 62, No. A, 8) gives off the following branches:
First, the hyoid artery (Fig. 72, No. 12) which supplies the inner portion of the depressor mandibular and also
the cornua of the os hyoideum, and extends to the tip of the tongue.
Second, the superior laryngeal artery (Fig. 72, No. 16) which supplies the sterno-brachialis and gives off
branches which extend downward to the trachea and to the esophagus. The main artery passes along the left side of
the esophagus and anastomoses with branches of the inferior esophageal, forming collateral circulation in that
region.

Fig. 62.

A. Blood-vessels of the head. 1, The cerebellum. 2. The
cerebrum. 3, The semicircular canals. 4, Sinus occipitalis
superior. 5, Sinus temporalis sphenoideus. 6, Sinus
transversus dexter. 7, Superior esophageal artery. 8, Carotis
externus. 9, Lingual artery. 10, Sinus longitudinalis.

B. Veins of the antero-inferior part of the head and neck. 1,
The right carotid artery. 2, The left carotid artery. 3, Vena
jugularis dexter. 4, Vena vertebralis dexter. 5, Transverse
vein. 6, Vena cephalica dexter anterior. 7, Vena lingualis. 8,
Vena cephalica posterior. 9, Vena facialis externa dexter. 10,
Vena infrapalatina. 11, Posterior nares. 12, Vena facialis
interna. 13, Vena facialis externa sinister.

C. The brain. 1, Medulla oblongata. 2, Cerebellum. 3, Optic
lobe. 4, Cerebrum. 5, Longitudinal fissure. 6, Transverse
fissure. 7, Olfactory nerve. 8, Optic nerve. 9, Optic
commissure. 10, Motor oculi. 11, Patheticus. 12, Trigeminal,
or trifacialis. 13, Abducens. 14, Facialis. 15, Auditory, or
acousticus. 16, Glosso-pharyngeus. 17, Pneumogastric. 18,
Spinal accessory. 19, Hypoglossus. 20, Hypophysis. 21, Crus
cerebri. 22, Ganglion on superior nerve trunk. 23, Spinal
cord. 24, A pair of spinal nerves.

Third, the lingualis artery (Fig. 62, No. A, 9) which lies between the mylo-hyoideus and the posterior part of
the hyoid bone. It supplies the tongue muscles. It passes to the median surface of the lower jaw bone, where are
given off small branches which enter the jaw and anastomose with the inferior alveolar artery.
Fourth, the Facial Artery.—The facial artery divides into the following branches:

The auricular artery is given off near the articulation of the os quadratum with the os zygomaticum. It is located
at the outer auditory canal, and its branches are distributed to the parotid region and to the depressor mandibular,
or digastricus, muscle.
The external facial artery is located between the os quadratum and the masseter muscle. It gives off a branch to
the lower jaw bone and to the skin of that region, and then passes to the lacrimal bone and supplies branches to the
commissure of the mouth, the auditory canal, the masseter muscle, the three eyelids (upper and lower eyelids and
the membrana nictitans), the nose cavity, and the skin in the frontal region. It communicates on the other side with
the ethmoidal artery.
The internal facial artery passes over and through the os pterygoideum, supplies all the jaw muscles, and is
continued as the inferior alveolar artery.
The inferior alveolar artery enters the canal of the lower jaw bone along with the mandibular nerve. It is finally
continued as the mental artery, leaving the canal, and passing to the outer jaw surface.
The facialis continues as the internal maxillary artery.
The internal maxillary artery (Fig. 72, No. 15) supplies the pterygoid muscle, the upper part of the pharynx, the
commissure of the mouth, the salivary gland region, the gums, and finally anastomoses with branches of the
spheno-maxillaris artery.

Branches of the Vertebral Artery

The vertebral artery is given off, dorsally near the thyroid gland, from the carotis communis or from the carotid
trunk. The vertebral artery passes horizontally and dorsally into the canals formed in the transverse processes of
the cervical vertebræ. After it leaves the carotid, it is divided into anterior and posterior branches.
The posterior vertebral artery passes in the canals of the transverse processes of the fifth or sixth dorsal
vertebra. It sends branches into the vertebræ, into the spinal canal, and into the intercostal muscles between the ribs
and anastomoses with the intercostal arteries.
The anterior vertebral artery is larger than the posterior. It extends laterally along the side of the neck in the
foramen of the transverse processes of the cervical vertebræ, and lies along the course of the inferior vertebral vein
and the deep imbedded trunk of the sympathetic nerve. It continues to the head. In its passage it gives off to each
vertebral segment a dorsal and a ventral branch. Twigs from these branches pass into the bodies of the vertebræ
and the spinal canal, giving nutriment to the bony structure and to the spinal cord and its coverings. Other twigs
are distributed to the muscles of the neck and some finally anastomose with branches of the carotis communis.
This artery, reaching the head, gives off a long anastomosing branch which passes between the atlas and posterior
part of the occipital bone and joins the ramus profundus and the occipital artery, thus again communicating with
the carotid artery. The remainder of the vertebral artery is small and passes through the foramen magnum into the
cranial cavity where it anastomoses with terminal branches of the cerebral artery. At the base of the neck and
before the vertebral artery enters the canal of the cervical vertebræ, it gives off the arteria cervicalis ascendens,
superior artery of the crop (Fig. 73, No. 18) which branches out on the upper surface of the crop is also distributed
to the neck muscles, and later subdivides into the transverse cervical arteries which supply the skin and the
muscles of the base of the neck, and the shoulder region.
On the ventral side of the neck there are given off two subvertebral carotid arterial branches. They lie in a
shallow furrow on the ventral side of the cervical vertebræ and close to the median line.

Branches of the Subclavian Artery

The subclavian artery (Fig. 20, No. 13; Fig. 73, No. 11) gives off the following branches:

1. Sterno-clavicularis (Fig. 73, No. 9) which originates on the upper part of the subclavia, between the carotid
artery and external thoracic (Fig. 73, No. 3), divides into many branches. The sterno-clavicularis gives off the
sternal artery, which enters by the side of the supra-coracoid muscle and the anterior rim of the sternum. It is
distributed to the inner surface and over the air-sac. Another outside branch passes the posterior end of the crista
sterna and supplies the large breast muscles.

The clavicular artery (Fig. 73, No. 8) accompanies the clavicle to the shoulder-joint.
The acromial artery is given off from the sterno-clavicularis on the ligament near the shoulder-joint.
2. The thoracic artery branches from the subclavian artery (Fig. 70, No. 4). The thoracic artery gives off the
following branches:
The internal mammary, or internal thoracic artery (Fig. 73, No. 16) arises on the inner side of the sternum and
extends downward and backward, giving nutrient branches to the anterior vena cava and to the diaphragm. At the
point of the costo-sternal muscle it divides into an inner and an outer branch.
The inner branch supplies the costo-sternal muscle and extends along the ribs and along their juncture with the
breast-bone. It finally extends posteriorly, giving numerous branches to the abdominal muscles. The outer branch
is distributed in a similar manner, giving off branches to the diaphragm and to the abdominal muscles, and
anastomoses, on the surface of the abdominal muscles, with the epigastric artery.
The external thoracic artery (Fig. 73, No. 3), ramus superior, supplies principally the large breast muscles.
The inferior thoracic artery, external ramus inferior, passes along the outside of the pectoralis major muscle,
extends downward, and gives off the arteria thoracica longa (subcutaneous thoracic). This latter artery supplies the
skin of the breast region. Other branches are given off to the muscles of the breast and to the skin of the region,
and some finally anastomose with the branches of the sternal artery.
3. The axillary artery (Fig. 73, No. 12) extends out of the thoracic cavity along with the brachial nerve plexus.
It gives off the subscapularis which supplies the muscles of the scapular region. The axillary artery terminates as
the brachialis which passes between the biceps brachii and anconeus muscles downward along the humeral shaft.
It gives off the anterior humeral circumflex artery and the brachialis profunda artery (Fig. 68, No. 3). It gives off
near the elbow-joint the ulnar and radial arteries.
The anterior circumflex humeral artery passes through the short head of the biceps and gives off a branch to the
biceps muscle, supplying the insertional part of the breast muscles.

Branches of the Brachialis Profunda

The brachialis profunda artery (Fig. 68, No. 3) continues as the posterior circumflex humeral artery. This artery
supplies the muscles of the posterior part of the humerus, the skin of the wing, and the muscles of the brachial
region. The trunk of the arteria brachii profunda passes downward along the anconeus muscle, supplying that
muscle and giving off the collateral ulnar artery. On the ulnar olecranon it anastomoses with the recurrent ulnar,
thus establishing, at this region, collateral circulation. The rest of the brachialis sends branches to the biceps
muscle and to the skin of the upper arm, and finally gives off the arteria collateralis radialis, which supplies the
condylo-ulnaris. It then anastomoses with the end branches of the recurrent radialis artery.
The radial artery (Fig. 67, No. 4) passes downward on the outer rim of the forearm. It continues down to the
carpal region, where it supplies the muscles and the skin of the carpal region it gives off the recurrent radial, which
passes on the middle finger and finally anastomoses with the collateral radialis artery.
The ulnar artery (Fig. 68, No. 6 and 9) passes downward on the inner surface of the ulna to the carpal region
where it gives off a branch to the wing plexus and divides into two branches, the smaller branch supplying the
thumb (Fig. 68, No. 7). This branch passes down the radial side of the middle finger to the last joint of the second
finger. The larger (Fig. 68, No. 8) lies between the second and the third finger bones, and passes through a slit
between these two bones to the flexor side of the hand and extends to the last finger-joint, supplying the structures
in the region. The ulnar artery gives off a small arterial twig to the papilla of each large wing feather (Fig. 67, No.
6).
The recurrent ulnar passes backward to the olecranon of the ulna and supplies the muscles, the skin, the
feathers, and other structures of the region, and terminates in end collateral ulnar branches (Fig. 67, No. 5).

BRANCHES OF THE POSTERIOR AORTA[7]

( Esophageal

( Intercostales

( Dorsal

( Lumbars

( Spermatics

( Renals

( Ovarian

( Celiac ( Recurrent esophageal

( axis ( Recurrent intestinalis ( Recurrent ilio-colicus

( ( Posterior or recurrent sinister ( Renalis

( ( Anterior or recurrent dexter ( Splenics

( ( ( Hepatic

( ( Hepatica dextra ( Gastric

(

Posterior ( Sacralis media ( Coccygeæ laterales

aorta ( ( Coccygea media ( Coccygeæ laterales

(

( Anterior mesenteric ( Recurrent ilio-celiacus

( ( Recurrent superior hemorrhoidal

( Posterior mesenteric ( Median hemorrhoidal

( ( Recurrent renalis

( ( Tibialis postica

( Ischiadica ( Tibialis antica ( Peroneal ( Anterior tibial plexus

( ( Arteria ovarialis

( Pudenda communis ( Renalis

( ( Hemorrhoidalis intima

( ( Pudenda externa

(

( Crural ( Internal pelvic (umbilical)

( (External iliac) ( Circumflex femoris

( ( Femoralis

7. Nomenclature used by Bronn.
The posterior aorta (Fig. 63, No. 2) passes backward along the inferior part of the bodies of the dorsal and
lumbo-sacral vertebræ. In the thoracic cavity it lies dorsal to the esophagus. It gives branches (esophageal) only to
the esophagus during its passage as far as the seventh dorsal vertebra. Following this point there are given of
several pairs of arteries which divide into a superior and an inferior branch. The superior branch extends upward
and anastomoses with branches of the vertebral artery and other twigs coming from the intercostal arteries. These
latter arteries given off are small dorsal arteries. The inferior branches extend downward between the ribs and
supply the intercostal muscles. The intercostal arteries do not take their origin from the aorta in numerous and
regular branches as in mammals; they consist originally of but few vessels, which are multiplied by anastomoses
with each other and with the arteries which come out of the spinal canal. An arterial plexus is thus formed around
the head of each rib, from which a vessel is sent to each of the intercostal muscles and ribs and are continued into
the muscles upon the outside of the body and its integuments. The anastomosis of the intercostal arteries round the
ribs is similar to the plexus, which is produced by the great sympathetic nerve in the same location. The lumbar
arteries are given off farther posteriorly and along the lumbar region. The lumbar, like the dorsal branches are
given off in pairs. These arterial branches pass along the thigh and the upper sacral vertebral region, and supply
those parts. Ventrally they are covered by the kidneys and pass into the abdominal muscles. The posterior aorta
gives off the spermatic arteries and the ovarian artery. In the male the former supply the testes. The ovarian artery
of the female gives off a twig to each calyx containing an ovum. Each calyx is voluminously supplied with blood.
Next the renal arteries are given off to the kidneys.

Fig. 63.—The vascular system injected. 1, The heart. 2, The posterior aorta. 3, The right brachio-cephalic artery. 4, The
left brachio-cephalic artery. 5, The anterior mesenteric artery showing its many branches and anastomoses near and on the
intestines. It is accompanied by branches of the mesenteric vein. 6, The rectal branch of the posterior mesenteric artery. 7,
The duodenal loop and pancreas showing the pancreatic artery. 8, The anus. 9, The cloaca. 10, The liver. 11, The lungs. 12,
The right subclavian artery. 13, The right carotid artery. 14, The right anterior vena cava. 15, The subclavian vein. 16, The
right jugular vein. 17, The carotid trunk. 18, The posterior vena cava.

Fig. 64.—The splanchnic arteries, veins and nerves. 1, A
portion of the left testes. 2, Adrenal gland. 3, Anterior lobe of
kidney. 4, Heart. 5, Liver. 6, Second portion of the
esophagus. 7, Proventriculus. 8, Gizzard. 9, Spleen. 10,
Duodenal loop. 11, Pancreas. 12, Blind extremity of cæcum.
13, Floating portion of small intestine. 14, Rectum. 15,
Cloaca. 16, Anus. 17, Celiac axis. 18, Ureter. 19, Vas
deferens. 20, Recurrent sinister artery. 21, Anterior recurrent
dexter artery. 22, Arteria hepatica dextra. 23, Recurrent
esophageal artery. 24, Recurrent intestinalis artery. 25, Ilio-
colicus artery. 26, Anterior mesenteric artery. 27, Recurrent
branches of the same. 28, Ilio-cœliacus artery. 29, Recurrent
superior hemorrhoidal artery. 30, Posterior mesenteric artery.
31, Crural arteries. 32, Sacralis media artery. 33, Recurrent
renalis. 34, Middle renal lobe. 35, Posterior renal lobe. 36,
Vena mesentericus communis. 37, Vena hemorrhoidalis. 38,
Vena pancreatico-duodenalis. 39, Vena proventriculo-
leinealis. 40, Vena portalis dextra. 41, Ischiadic nerve. 42,
Thoracic sympathetic trunk. 43, Anterior splanchnic plexus.
44, Spinal nerves. 45, Posterior splanchnic nerve plexus. 46,
Intestinal nerve trunk. 47, Vena renalis magna.

The celiac axis (Fig. 64, No. 17) originates near the seventh sternal vertebra and to the right of the esophagus,
breaks through the diaphragm, and, near this point, gives off a recurrent esophageal (Fig. 64, No. 23). The celiac

axis gives off three main branches: The anterior or recurrent dexter, the posterior or recurrent sinister, the recurrent
intestinalis, all of which lie to the right of the spleen, under the left lobe of the liver, and along the left side of the
stomach. The recurrent sinister (Fig. 64, No. 20) gives arterial branches to the proventriculus, the gizzard, the
pyloris, and the left lobe of the liver. The anterior or recurrent dexter (Fig. 64, No. 21) gives off a renal artery and
from four to six splenic arteries.
The recurrent intestinalis artery (Fig. 64, No. 24) arises on the posterior of the stomach within the duodenal
loop, and supplies the duodenum and the pancreas (Fig. 63, No. 7). It gives off a branch, called the recurrent ilio-
colicus (Fig. 64, No. 25), which supplies the large intestines, including the cæca.
The arteria hepatica dextra (Fig. 64, No. 22) is a branch from the celiac axial trunk. It gives several branches to
the right lobe of the liver and to the gall-bladder. The gastric branches pass to the muscles of the stomach. The
anterior and posterior recurrent branches often anastomose.
The anterior mesenteric artery (Fig. 63, No. 5; Fig. 64, No. 26) originates from the posterior aorta near the
generative glands. It is directed downward, and divides into many branches which pass in the mesentery toward
the intestines. Recurrent branches (Fig. 64, No. 27) are given off, which anastomose, forming mesenteric arches.
From these arches are given off branches which supply the intestinal walls.
The anterior mesenteric artery gives off the recurrent ilio-celiacus (Fig. 64, No. 28) which is distributed to the
cæca; other of its branches are distributed to the small intestine.
The anterior mesenteric artery extends along the small intestine and ends in the recurrent superior hemorrhoidal
arteries (Fig. 64, No. 29) which anastomoses on the surface of the rectum with a branch of the posterior
mesenteric artery.
Branches from the anterior mesenteric artery also anastomose with branches of the celiac axis.
The posterior mesenteric artery (Fig. 64, No. 30) is given off from the posterior aorta posterior to the origin of
the anterior mesenteric and near the arteries of the thigh and is distributed to the lesser mesentery supplying the
large intestine. Branches of the superior hemorrhoidal arteries anastomose with branches of the posterior
mesenteric artery. Branches from this source are called the median hemorrhoidal (Fig. 63, No. 6).
The posterior mesenteric artery (Fig. 64, No. 30) also gives off a long branch to the cæca. Branches of the
posterior mesenteric artery anastomose with branches of the anterior mesenteric.
The crural arteries (Fig. 64, No. 31) are given off in a pair from the posterior aorta. They pass through the
mass of the lobes of the kidneys, at about the median region, and extend out of the pelvic cavity in front of the
spine and ilio-pubic ligament.

Fig. 65.—Blood-vessels and nerves of the hind extremity. Inside view of leg. 1, Ischiadic nerve. 2, Ischiadic artery. 3,
Posterior tibial vein. 4, Vena metatarsa dorsalis interna. 5, Vena metatarsalis plantaris profunda. 6, Vena cruralis. 7, Vena
metatarsalis interna, vena magna. 8, Vena tibialis postica. 9, Vena metatarsa magna. 10, Nerves of the toes. 11, Vena
metatarsalis dorsalis profunda.

The crural, or the external iliac artery, is divided into three branches as follows:

First, the internal pelvic, or umbilical artery, is given off just as the cruralis leaves the pelvic cavity. It passes, as
a long vessel, on the inner surface of the lumbo-sacral bones and supplies the obturator internus muscle and
extends into the umbilical region. It gives off branches to the abdominal muscles, and, in the female, a branch is
distributed to the ligament of the oviduct.
Second, the arteria circumflex femoris, which passes between the sartorius and vastus internus and extends
dorsalward, supplies the sartorius muscle, the vasti muscles, and the ilio-trochanteric region.
Third, the femoral artery, which passes beside the vena cruralis and extends down the posterior surface of the
thigh to the knee-joint, supplies the upper thigh muscles with the exception of the adductor muscles.

Fig. 66.—Blood-vessels and nerves of the posterior extremity. Outside view. 1, Anterior tibial artery. 2, Metatarsal artery.
3, Digital arteries. 4, Vena cutaneous crurus. 5, Ischiadic artery. 6, Vena cruralis. 7, Lateral cutaneous branch of the
ischiadic nerve.

Fig. 67.—Blood-vessels and nerves of the fore limb. Outside view. 1, Median nerve. 3, Ulnar nerve. 4, Radial artery. 5,
Recurrent ulnaris artery. 6, Twigs of ulnar artery to wing feathers.

The ischiadic artery (Fig. 69, No. 9) forms the main artery of the posterior extremity. This artery, the largest
vessel of that region, is given off from the posterior aorta and passes ventrally over and between two of the main
lobes of the kidney. The continuation of the posterior aorta is called the sacralis media (Fig. 64, No. 32). The
ischiadic artery gives off a recurrent renalis on the posterior lobe of the kidney (Fig. 64, No. 33). On the left side it
gives off a branch to the oviduct and to the ligament of the oviduct. The main trunk leaves the cavity with the
ischiadic nerve (Fig. 65, No. 1) through a foramen formed by the os ilium and the os ischium. It sends branches
into the adductor muscles of the upper and the lower thigh. It gives off anastomotic branches which unite with
those from the femoral artery. At the flexure of the knee-joint it gives off two branches to that region (Fig. 69, No.

10). It gives off another branch to the gastrocnemius muscle and one to the flexor perforans digitorum. It
terminates in the anterior and posterior tibial arteries.

Fig. 68.—Blood-vessels and nerves of the fore limb. Inside view. 1, Vena humeri profunda. 2, Brachialis longus inferior. 3,
Brachialis profunda. 4, Radial artery. 6, Ulnar artery. 7, Ulnar arterial branch to thumb. 8, Digital branch of ulnar artery. 9,
Ulnar artery.

The first, the tibialis postica (Fig. 69, No. 12) passes between the gastrocnemius and the deep flexors giving off
branches in its course to the skin and to other parts, and disappears shortly below the intertarsal joint.
The second, the tibialis antica (Fig. 66, No. 1; Fig. 69, No. 11), is often the larger of the two arteries. The
anterior tibial artery gives off branches to the knee-joint and to adjacent structures. It gives a large branch to the
head of the gastrocnemius muscle. It passes to the posterior surface of the tibial head and gives off the peroneal
artery, which passes through the membrana interossea located between the tibia and fibula giving branches to the
anterior side of the membrane of the patellar region of the knee-joint. It gives branches to the anterior side of the
lower thigh and finally terminates subcutaneously in the anterior tibial plexus.
The main portion of the anterior tibial artery passes downward along the posterior surface of the membrane
located between the tibia and fibula, and sends branches for the flexor digitorum communis et profundus. It then
breaks through the membrane, reaches the anterior side and there communicates with the anterior tibial plexus. It
gives off branches to the muscles on the anterior side of the lower thigh and the skin, and passes between the outer
and the middle malleolus of the tarsal bones. It passes to the plantar surface and divides between the toes. In
addition to the plantar branches there are given off dorsal branches between the third and the fourth toes. These
branches form the direct continuation of the dorsal vessels of the anterior tibial plexus.

Fig. 69.—Blood-vessels and nerves of the femoro-tibial region. A section of the tibia removed.

A. Veins, arteries and nerves dissected as in B.

B. V, Vein. A, Artery. N, Nerve. 1, Vena poplitealis. 2, The three veins forming the vena poplitealis. 3, Vena femoris interna
profunda. 4, Vena femoris anterior. 5, Vena cruralis. 6, Vena cutanea abdominalis femoralis. 7, Vena cutaneous cruralis. 8,
Deep vein of the knee-joint. 9, Ischiadic artery. 10, Branches of ischiadic artery to flexure of knee. 11, Anterior tibial
artery. 12, Posterior tibial artery. 13, Ischiadic nerve. 14, Trunk (a branch of the ischiadic) which gives off the superficialis
peroneus and peroneus profundus. 15, Median branch of ischiadic nerve. 16, Superficialis peroneus. 17, Lateral branch of
the ischiadic nerve.

The arteria pudenda communis (Fig. 70, No. 20) passes to the depressor coccygeus muscle, gives off a branch
to the caudal part of the kidney, crosses the ureter, provides the ischio-pubic and pubio-coccygeus, or depressor
coccygis lateralis, muscles, and on the lateral rim of the latter muscle it gives off the arteria hemorrhoidalis
intima. This artery passes to the bursa of Fabricius and to the end of the cloaca. It enters into the ischio-coccygeus
muscle, and divides into the arteria pudenda externa, and in ducks, the arteria profunda penis. These branches
supply the vas deferens, the ureter, the cloaca, the penile structure, and the muscles of these parts.

Fig. 70.—Blood-vessels of a Cornish cock. 1, The left pulmonary artery. 2, Right pulmonary artery. 3, Left brachio-
cephalic artery. 4, Left subclavian artery. 5, Left carotid artery. 6, Right brachio-cephalic artery. 7, Posterior aorta. 8,
Posterior vena cava. 9, Left pulmonary vein. 10, Right pulmonary vein. 11, Celiac axis. 12, Anterior mesenteric artery. 13,
Ischiadic artery. 14, Crop. 15, Superior artery of the crop and vein of same name. 16, Testicular or ovarian artery. 17,
External iliac artery. 18, Intercostal nerve. 19, Median sacral artery. 20, Arteria pudenda communis. 21, Anus. 22, Vena
hypogastrica. 23, Right vena hepatica magna. 24, Left vena hepatica magna. 25, Vena iliaca interna. 26, Vena iliaca
communis. 27, Vena iliaca externa. 28, Vena coccygo-mesenterica. 29, Vena umbilicalis. 30, Vena suprarenalis. 31, Origin
of the pars renalis. 32, Lumbar veins. 33, Vena epigastrica. 34, Lumbales (arteries). 35, Anterior division of the lumbo-
sacral plexus. 36, Posterior division of the lumbo-sacral plexus. 37, Left anterior vena cava. 38, Right anterior vena cava.

The Sacralis Media.—The median coccygeal artery (Fig. 70, No. 19) forms the single extension of the sacralis
media. It gives off lateral branches between the caudal vertebræ which supply the dorsal muscles of that region and
the skin. The third pair are the largest. These are the arteriæ coccygeæ laterales, and are located on the dorsal side
of the tail, they supply the tail glands and rudder feathers, the main tail feathers, or rectrices. A small arterial twig
is given off to the papilla of each rectrix.

The Venous Trunks

The venous blood enters the lungs from the right ventricle through the two pulmonary arteries (Fig. 70, No. 1
and 2).
The two pulmonary veins (Fig. 70, No. 9 and 10) collect the arterial blood from the lungs, and empty it into the
left auricle.
There are three venæ cavæ which collect the systemic blood and empty it into the right auricle. These venæ
cavæ are two anterior (Fig. 70, No. 37 and 38) and one posterior (Fig. 70, No. 8).
Each anterior vena cava is formed by the union of a vena jugularis, a vena vertebralis, and a vena subclavicularis
(Fig. 63, No. 15).

Fig. 71.—Veins of the liver of a fowl. 1, Vena mesenterica communis. 2, Vena portalis propria. 3, Anterior vena
mesentericus. 4, Vena portalis dexter. 5, Vena portalis sinister. 6, Posterior vena cava. 7, Celiac axis. 8, Base of the heart. 9,
The liver. 10, Hepatic veins.

The jugular vein is formed by the union of the vena cephalica anterior, and the vena cephalica posterior.
The jugular vein (Fig. 62, No. B, 3) passes along the side of the neck and lies near the trachea, the esophagus,
and the pneumogastric nerve. Near the base of the skull the two jugular veins, the right and the left, are connected
by a transverse vein. By this anastomosis part of the blood from the left jugular vein is sent into the right.
Therefore the right jugular vein is larger than the left. The jugular veins collect the blood from the tongue region,
the thyroid, the esophagus, the trachea, the crop, and other structures along its course through the cervical region.
The vertebral veins are divided into the anterior and the posterior, or the inferior and the superior. The anterior
vertebral vein is located in the cervical region and collects the blood from the brain and the inner part of the head.
The vertebral vein passes along the dorsal side of the spinal cord.

BRANCHES OF THE VENÆ CAVÆ ANTERIORES

( Venæ linguales

( Vena occipitalis lateralis ( Vena occipito-collores

( Vena ascendenes lateralis

( Venæ colli cutineæ

( Venæ esophagealeæ

( Venæ tracheales

( Vena ( Vena subscapularis

( jugularis ( Venæ glandularum thyroidearum

( ( ( Vena occipitalis ( Sinus foraminis

( ( ( interna ( occipitalis

( ( Vena (

( ( vertebralis ( Vena vertebralis posterior ( Vena intercos

Vena cava ( ( ( Vena vertebralis anterior

anterior ( ( Vena vertebralis

( Vena vertebralis lateralis dorsalis ( Venæ intercostales

(

( Venæ coronariæ

( Vena subclavicularis

( Vena thoracica interna ( Vena intercostales

( Vena pharyngea superior

( Vena muscularis depressoris mandibularis

Vena facialis ( Vena muscularis colli anterior superioris

communis ( Vena lingualis

( Vena sublingualis et sphenoidea

The posterior vertebral vein is located in the dorsal region, passes backward and receives the blood from the
dorsal neck region and from the intercostal veins and from the vertebral segments and adjacent regions.
The anterior and the posterior vertebral vein form one trunk, the vertebral vein, and this trunk empties into the
vena jugularis just before the subclavian and the jugular unite.
The subclavian vein collects the blood from the anterior extremities. It unites with the vena jugularis of the
same side.
The left vena cava receives the coronary veins from the heart.

THE VEINS OF THE HEAD

Branches of the Vena Facialis Interna

The vena facialis interna (Fig. 62, No. 12) lies dorsal on the pterygoid bone and receives the vena maxillaris,
the vena ophthalmica, the vena mandibularis interna, the venæ pharyngeæ superiores, and the vena retis mirabilis
temporale.

Fig. 72.—Blood-vessels and nerves of the abdominal cavity
and hind extremity and head. 1, Vena renalis. 2, Vena
intervertebrales sacrales. 3, Posterior aorta. 4, External iliac.
6, Ischiadic nerve. 7, Ischiadic artery. 8, Arterial rete (plexus
temporalis). 9, Ophthalmic artery. 10, Palatine artery. 11,
Lingual artery. 12, Hyoid artery. 13, 14, External carotid
artery. 15, Internal maxillary artery. 16, Superior laryngeal
artery. 17, Superior esophageal artery. 18, Occipital artery.
19, Internal carotid artery.

The vena maxillaris comes out of the upper beak with the recurrent trigeminus nerve and then passes backward
between the jugular and palatine bones. It lies medio-ventrally to the eyeball and communicates at this point with
the ophthalmic vein. It is covered ventrally with the pterygoid bone. The maxillary vein collects the blood from the
gland of Harder, the upper beak, and receives blood from the vena supra-palatina and from the lower jaw bone
and the external mandibular vein. It also receives blood from the external sublingual vein, and the sublingual
gland. It follows the inner rim of the jaw bone. The maxillary vein receives an anastomosing branch from the
cutaneous facial vein, at a point near the commissure of the mouth.

Fig. 73.—Photograph of blood-vessels and nerves of the
thorax. 1, Vena sternalis. 2, Vena thoracico-externa. 3,
External thoracic artery. 4, Coracoid bone. 5, Sternum. 6,
Shoulder-joint. 7, Humerus. 8, Clavicularis artery. 9, Sterno-
clavicularis artery. 10, Thoracico-humeralis artery. 11,
Subclavian artery. 12, Axillary artery. 13, Brachialis
profundus artery. 14, Ulnar artery. 15, Radial artery. 16,
Internal mammary artery. 17, Superior vein of the crop. 18,
Superior artery of the crop. 19, Brachial nerve plexus. 20,
Anterior division of brachial nerve plexus. 21, Posterior
division of brachial nerve plexus.

The vena ophthalmica lies close to the point where the olfactory nerve passes out of the cranial cavity. The
largest branch it receives is the recurrent ophthalmo-temporalis, which accompanies the lateral side of the optic
nerve. It collects the blood from the base of the brain, from Harder’s gland, from the eye muscles, from the inner
eye, the nose, the lacrimal gland, the skin of the frontal region, and the comb.

BRANCHES OF THE VENA JUGULARIS

( Vena maxillaris

( Vena ophthalmica

( Vena facialis ( Vena mandibularis interna

( interna ( Vena retis mirabilis temporalis

( Vena cephalica ( ( Venæ pharyngeæ superiores

( anterior or (

( facialis ( ( Vena facialis cutinea

( communis ( ( Vena temporalis

( ( Vena facialis ( Vena auricularis

Vena jugularis ( ( externa ( Vena palpebralis

or cephalica ( ( Vena transvers

communis ( ( Vena retis m

( Vena subclavia

( Venæ vertebrales

( ( Sinus cranii et cerebri

( ( Vena carotis

( (

( ( Vena auris ( Sinus foveæ cerebelli

( ( ( Vena occipitalis ext

( Vena cephalica ( Vena jugularis prima

( posterior ( Vena occipitalis

( Vena lingualis

( Vena mandibularis externa

Vena maxillaris ( Vena sublingualis externa

( Vena supra-palatina

Vena ophthalmica ( Vena ophthalmo-temporalis, recurrent

Vena facialis communis ( Vena cephalica externa

Vena occipitalis externa ( Vena occipitalis interna

Vena retis mirabilis temporalis ( Vena spheno-temporalis

Sinus foveæ cerebelli ( Sinus occipitalis externa

The trunk of the internal facial vein receives the blood of the internal mandibular vein. The internal
mandibular vein emerges from the alveolar canal of the inferior jaw bone and receives branches from the muscles
of mastication.
The vena retis mirabilis temporalis passes out of the eye cavity and lies between the internal facial vein and
the external facial vein, and passes around the os quadratum and the os pterygoideum. It receives veins from the
outer ear region, lacrimal gland, eyelids, and the spheno-temporalis.
The venæ pharyngeæ superiores are the veins on the dorsal surface of the pharynx. These veins form the small
plexuses which unite with the two trunks of the facial veins. This forms an anastomosis between the left and the
right facial veins.

Branches of the External Facial Vein

The vena facialis externa (Fig. 62, No. B, 9) lies behind the quadrate bone and is partly covered ventrally by the
inner extension of the lower jaw bone. It collects the blood principally from the upper region of the cranium and
the face, including the comb.
The vena facialis cutinea receives branches from the muscles in the region of the jaw, the lower jaw bone, the
muscles of the eyelids, the frontal region, and the anastomotic branches from the vena maxillaris.
The vena temporalis is made up of veins from the skin of the temporal region, the masseter and the tongue
muscles, and from the sides of the upper throat region.
The vena palpebralis is made up from veins from the three eyelids and the temporal region near the eye. Its
trunk passes laterally over the temporo-mandibularis ligament. The vena palpebralis collects blood from the

lacrimal gland, the eyelids, and the outer ear region.
The following veins empty into the trunk of the vena facialis communis: venæ pharyngis superiores, vena
muscularis depressoris mandibulæ, vena muscularis colli anterior superioris, vena lingualis et hyoidea. The right
terminal branches of the vena lingualis empty into the vena cephalica posterior.
The venæ pharyngis superiores and vena lingualis et hyoidea collect blood from the muscles of the tongue and
posterior tongue region.
The vena lingualis et hyoidea (Fig. 62, No. B, 7) collects the blood from the muscles of the tongue region, the
lower tongue glands, and the upper throat region.
Between the two trunks of the vena facialis communis and anterior to the entrance of the vena cephalica
posterior there is an anastomosis, the vena transversus (Fig. 62, No. B, 5). Through this anastomosis which lies
crosswise the two jugular veins are influenced in different ways. At this point both jugular veins are of the same
size. The anastomotic branch lies crosswise. Through this anastomosis the right receives some blood from the left
head region indicating that the blood flows from left to right. This, as stated before, makes the left jugular vein the
smaller.

Branches of the Vena Cephalica Posterior

The left vena cephalica posterior (Fig. 62, No. B, 8) communicates with the transverse vein (Fig. 62, No. B, 5).
The left receives the smaller veins of the skin region, the esophagus, and the trachea. These vessels communicate
with their fellow of the opposite side and with the vertebral vein of the same side, which causes a gradual
reduction of the size of the jugular vein.

BRANCHES OF THE VENA OCCIPITALIS EXTERNUS

( ( Venæ choroideæ

( Sinus ( Venæ cutaneæ et frontales

( longitudinalis ( Venæ nasales

Vena ( ( Venæ ophthalmiæ

occipitalis (

externus ( ( ( Sinus occipitalis

( Sinus ( Sinus ( Sinus temporo-sphenoideus

( semicircularis ( transversus ( Venæ cerebellares

( ( ( Sinus petrosus sphenoideus

Sinus petrosus sphenoideus ( Retis mirabile temporalis

Sinus temporo-sphenoideus ( Sinus annularis venosus basilaris

Sinus foraminus occipitalis ( Venæ medullares

( Venæ cerebrales

Sinus ( Vena cerebralis basilaris ( Sinus venosus annularis anterior

venosus (

annularis (

basilaris ( Vena ophthalmica

( Vena medullaris mediana longitudinalis

The vena cephalica posterior (Fig. 62, No. B, 8) is formed from the veins of the sinuses of the cranium, the
brain, the vena auris, the vena jugularis prima, the vena carotis, and the vena occipitalis. It collects most of the
blood from the cranium and the posterior part of the head and from the tongue.

THE VENOUS SINUSES OF THE HEAD

The sinus longitudinalis (Fig. 62, A, 10) extends from the dorsal median line of the internal occipital
protuberance to the olfactory nerve. It collects the blood from the choroidea of the brain and from the skin of the
frontal region. It receives laterally the veins of the nose, the vena ophthalmica, and the sinus transversus.
The sinus occipitalis (Fig. 62, No. A, 4) forms the continuation of the transverse sinus. It is located in the
posterior cerebral cavity, and is wing-shaped, extending both to the right and to the left.
The sinus foraminis occipitalis a continuation of the sinus occipitalis, lies transversely on the ventral side of
the cranial cavity and receives the veins from the medulla oblongata. One branch passes through the os occipitalis
basilare, and then extends sidewise to the foramen magnum and anastomoses with the vena occipitalis.
The sinus transversus (Fig. 62, No. A, 6) extends in a pair from the internal occipital protuberance between the
cerebrum, cerebellum, and the corpus quadrigeminum. It receives vessels from the upper surface of the
cerebellum. The sinus has three branches, all of which empty into the sinus semicircularis.
The sinus semicircularis extends along the dorsal petrosal rim, anterior to the inner ear, and from this point
backward. Near the foramen magnum it passes through the os occipitale and empties into the external occipital
vein.
The vena occipitalis externus extends near the foramen magnum, surrounds the basis occipitalis, and receives
the semicircular sinus and through the semicircular sinus the blood from the sinus transversus.
The sinus petrosus sphenoideus, passing in company with the occipital sinus, extends from the transverse sinus
to the cavity near which the trigeminus lies. The sinus dividing into two branches, one of these extends to the
hypophysis and unites with the basal veins of the brain; the other passes with the rete out of the cranial cavity
along with a branch of the trigeminus, and communicates with the rete mirabile temporale.
The sinus temporo-sphenoideus (Fig. 62, No. A, 5) extends forward and outward from the transverse sinus,
and, between the corpus quadrigeminum and the cerebrum, unites with the sinus venosus annularis basilaris.
The sinus venosus annularis basilaris lies in the region of the optic nerve and surrounds the hypophysis,
forming a complete circle. It receives small vessels from the cerebrum, the corpora quadrigemina, and anteriorly
the longitudinal basilar vein or vena basilaris media, of the cerebrum, which comes out of the anterior annular
venous sinus. The anterior annular venous sinus surrounds the base of the olfactory nerves. It communicates with
the sinus petrosus sphenoideus, which emerges from behind the optic lobe, the sinus temporo-sphenoideus, which
emerges from in front of the optic lobe, and posteriorly the median longitudinal vein of the medulla oblongata or
vena basilaris. Laterally and anterior to the optic lobe it receives the vena basilaris lateralis, and also a branch of
the vena ophthalmica.
The blood received by the sinus annularis basilaris comes from the brain cavity through three pairs of veins, as
follows: first, the two ophthalmic veins which pass through the posterior orbital wall between the olfactory and the
optic nerve; second, two other branches of the ophthalmica which pass with the optic nerve; third, two veins which
pass through a foramen by the side of the sella turcica to the hypophysis together with the carotis cerebralis, and
then leave the cerebral cavity ventrally, at which point they are called the venæ carotes. These last accompany the
cerebral artery backward, and pass through a foramen in the base of the cranium. Each one then passes through the
cranial wall close to the external auditory canal, and empties into another vein in the posterior region of the head.
The sinus fovæ hemispherii cerebelli lies in the hollow between the os petrosum and the semicircular canals. It
receives blood from the external occipital sinus and from the cerebellum, and empties into the vena auris interna.