Chapter I: 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.

Footnote 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.