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VETERINARY SCIENCE ASSOCIATION
OF AMERICA

NOTES ON VETERINARY ANATOMY

BY

CHARLES J. KORINEK, V. S.

Graduate of the Ontario Veterinary College, in affiliation with the University of Toronto, Canada. Hon. Member of the Ontario Veterinary Medical Society. Ex. State Veterinarian for Oregon. Ex. President of the Oregon State Veterinary Medical Board of Examiners. Author of “The Veterinarian”. Principal of the Veterinary Science Association of America. Sixteen years of Practical Experience as a Veterinary Surgeon.

PUBLISHED BY THE

VETERINARY SCIENCE ASSOCIATION
OF AMERICA

COPYRIGHT 1917
by the
VETERINARY SCIENCE ASSOCIATION
OF AMERICA

TABLE OF ILLUSTRATIONS.

TABLE OF ILLUSTRATIONS.

TABLE OF CONTENTS.

PREFACE

There are a number of excellent works on Veterinary Anatomy, and many of them will amply repay the student for the time taken to master them, but for quick reference none seem to contain the wants of the veterinary practitioner and student for which this humble little work is primarily intended.

It has been my endeavor to briefly describe each organ as found in the healthy animal; its functions, etc., in a condensed yet complete form. I am positive that the student or veterinary practitioner will find its pages highly instructive as well as profitable and interesting.

In compiling this work a few authorities have been consulted and quoted, while it has not been practical to give individual credit for the use of ideas and language, a general acknowledgement is here made:

Veterinary Science, Hodgins and Haskett.

Veterinary Anatomy, Strangeways.

Charles J. Korinek, V. S.

DESCRIPTIVE ANATOMY

Osteology is a term applied to that section of descriptive anatomy which treats of the bones. Arthrology, to the consideration of the joints or modes of union between the bones, while by Myology is meant the doctrine of the muscular system. Splanchnology treats of the viscera, Angiology of the circulatory and absorbent systems. Neurology deals with the nervous system. Aesthesiology with the organs of sense; while Embryology, as before stated is the consideration of the animal frame at periods preceding its birth.

In this work the various departments are discussed in the order here given. The structures which are the subject of the first three divisions are sometimes classed together as the Organs of Locomotion; for bones form the frame work of the body and often act as levers; the joints connect the bones, permitting more or less motion between them; while the muscles move the bones, and so produce motion of a part of the body—or it may be locomotion, or change of situation in the entire frame.

In the study of comparative Anatomy the terms analogy and homology are frequently met with. Although these words are unfrequently used indiscriminately, the following differences should be noted. Organs are said to be analogous when, though differing in structure, they perform the same function; but when their functions are different, which, in the broad sense, they correspond in structure or form, they are said to be homologous. Thus the middle finger of the human hand is the homologue of the anterior (front) digit of a horse, because they have the same general structure, and relation to the rest of the limb; but as the functions they perform are quite dissimilar, they cannot be termed analogous. Again, the lungs of a mammal are analogous to the gills of a fish, for, though they differ widely in structure, position and form, and are therefore not homologous, their ultimate use is the same—each of them being an apparatus in which is carried on the process of purifying the blood.

DISSECTION.

Students must dissect as many animals as possible, so as to familiarize themselves with the frame work or structure, and the location of the digestive, nervous and blood systems, as it will aid materially in the art or process of determining the nature of various diseases.

During cool weather an animal for dissecting purposes can be kept for a considerable length of time without preservatives

It is well to have a copy of Anatomy at hand when dissecting for it will show the location of the various organs and explain their functions.

SKELETON OF HORSE—AFTER MEGNIN.

EXPLANATION OF PLATE I

Skeleton of the Horse

CHAPTER I.

OSTEOLOGY.

Structure of the Bones—Bones are hard, yellow-white, insensitive objects, which form the skeleton and give attachment to soft structures (muscles, tendons and ligaments); they are of various sizes, forms and densities. In the limbs the bones are ordinarily more or less long, circular bodies, with expanded ends, effectually supporting the body, supplying leverage and attachment for soft structures, and forming the basis of all joints. Where cavities, such as the cranium, chest, and pelvic, enclosing the organs requiring protection and support, the bones tend to assume a flat, expanded form.

Living bone is bluish pink, insensitive, and elastic; on exposure to air it becomes diseased and blackened, very sensitive and painful; (the teeth excepted) which are harder and of a higher specific gravity than any other bone formation.

Bones are composed of two kinds of substance—animal, which makes the bone tough and flexible; earthy, which makes it hard and fragile. In young animals the animal matter forms about one-half of the bone substance; in the adult, it diminishes to about a third, while in old animals it is still less; hence the bones of very old animals are brittle, more liable to fracture and harder to mend.

Bones in a six-year-old horse contained, Phosphate of Lime, 54.37 per cent; Carbonate of Lime, 12.00 per cent; Phosphate of Magnesia, 1.83 per cent; Soluble Salts, 0.70 per cent, or mineral matter, 68.90 per cent. While they contain Cartilage, 27.99 per cent; Fat, etc., 3.11 per cent, or animal matter 31.10 per cent.

In bone tissue there are two modifications of texture, the compact and the cancellated. The former—hard, dense, and ivory-like, is always situated externally; the latter porous and spongy lies within.

Although the compact tissue appears uniformly dense, and destitute of porosity, yet, if we transversely sectate the shaft of a long bone, and examine it under the microscope, by transmitted light, it is found to contain numerous round openings. These are called Haversian canals. They transmit bloodvessels, and run in a longitudinal or slightly oblique direction, opening on either the outer or inner surface of the bone.

The external (outer) surface of every bone is covered by a tough, fibrous, inelastic membrane called periosteum, which can be seen by examining the bone of an animal which has recently died. The only exception to this is at the joints where one bone articulates with another, and where a tendon or muscle plays over a bone; here we find its place taken by articular cartilage. By its strength it sometimes retains bones in contact after an oblique fracture; in the young, it is thicker and more vascular than in the adult. Blood-vessels which penetrate the periosteum pass directly to the bone; the outer surface of the bone is always studded with numerous foramina through which these enter.

The periosteum owing to its inelasticity, is, when inflamed, the seat of intense pain; and should any part of it be stripped off, there is every probability of the denuded bone dying and separating.

Contents of Bone.—Red marrow is found in the extremities or near the ends of bones, white marrow is found in the shaft.

Classes of Bones.—Bones are classed as long, flat, and irregular. Long or cylindrical bones are found in the limbs or extremities, and serve as levers and pillars for traveling and to support the body. Descriptively, a long bone is divisible into a center or shaft and two ends or extremities. Flat bones are found where visceral organs need protection. As the shoulder or scapula and ribs, to protect the heart and lungs; pelvic or hip bones, to protect the rectum and urinary and genital organs; also the cranial bones, to protect the vital organ called the brain. Irregular bones are found in the spinal column and in the joints, such as the knee or carpus, hock or tarsus, where great strength is required. They usually possess many angles and indentations, with surfaces for articulation and tendonous attachment, and consist of a thin, dense, external (outer) case of compact bone enclosing cancellated tissue. In proportion to their size they present a much larger extent of articular surface and greater mechanical strength than any other class.

1. Skull, or skeleton of the head, the most anterior (forward) part of the horse’s skeleton, articulates with the first cervical vertebra (or atlas), from which it is suspended by its posterior (or back part) extremity, its anterior (forward) extremity being free. Its position varies with the attitude of the animal; but in our descriptions we shall always suppose it to be placed in a horizontal position.

In the young animal the skull is composed of a number of bones, all of which, with the exception of the lower jaw, the teeth, the bones of the tongue, and ossicles of the ear, become united by ossification (growing together) in the adult.

In speaking of the different points of importance in connection with the head bones of the horse, and other animals, suppose a cross or longitudinal section of the head is made. It will be noticed that it is full of cavities or sinuses. The uses of these are to lighten the head and also to warm the air as it passes into the nostrils, on its way down to the lungs. It will also be found full of foramen or small holes through which the nerves from the brain and various blood vessels pass to the organs situated in the head, such as the tongue, lips and the various glands in and around the head.

Then there are the cavities in which the eyes are situated, one on each side of the head, called the orbital fossa. In examining this fossa you will find a small opening or foramen, through which the optic nerve passes in coming from the brain to the eye. This is the nerve of sight. Then the most important part of all to consider is the cranial cavity in which that very important organ is situated called the brain, which controls all the various functions and movements of the body.

Another important point is the situation of the ear drum. It is situated in the hardest bone found in the whole skeleton, called the petrosal. The nerve that gives the function called hearing comes from the brain down to the petrosal bone and enters by a small foramen or hole into the drum of the ear to give hearing. This nerve is called the auditory nerve.

2. Cervical Vertebrae or Neck Bones.—These bones are seven in number. The first and second bones proceeding from the head receive special names. The first one is called the atlas, from which the head is suspended and to which it is attached; it somewhat resembles the body of a bird with wings extended. The second bone receives the name of dentata. This is the bone which allows the head to turn in any direction, hence it is sometimes called the axis or pivot of the neck. Between these two bones, on the upper surface, is the only place where the spinal cord is not covered with bone, a spot about three-fourths of an inch in diameter. The next four bones receive no name, and are about the same in size and length. The last, or the seventh bone, is only about one half the length of the preceding ones and receives no special name.

3. Dorsal Vertebrae or Back-Bone.—Dorsal bones are eighteen in number. The chief point of interest about them are the height of the spines on the upper surface of the bones. These large spines form the withers of the horse, as will be noticed in the skeleton. On either side of these bones the ribs are attached, 18 pairs corresponding with the number of bones in this region.

4. Lumbar Vertebrae (or the bones which form the skeleton of the loins). These bones are six in number, and they are situated immediately above the kidneys.

5. Sacral Vertebrae or Rump Bones.—There are five of these bones in the young horse, but in the adult they unite as a single bone, somewhat triangular-shape. These are situated between the upper hip bones and help to form the rump. Beneath these bones the bladder is situated.

6. Coccygeal Vertebrae or Tail Bones.—These are 18 to 20 in number. There is no complete canal, like in the previous vertebraes, for enclosure of the spinal cord.

7. Pelvic or Hip Bones.—The pelvic bones are flat, but somewhat irregularly-shaped, and they form the sides, floor, and part of the roof of the pelvic cavity. Above they are connected with the sacrum, and below united to each other, in the adult, by ossification (union of bone). In the young animal, as above stated, and especially in the foetus, each side consists of three parts, which retain their names of ilium, ischium, and pubis, even after union by ossification. They all three meet in the acetabulum, or articular cavity for the femur or hip bone.

8. Sternum or Breast Bone.—This bone is small and short in the horse and is situated on the lower surface of the chest cavity. The principle points to be noted in this bone are that of its softness, and that the first eight pairs of ribs are attached to it on either side. This bone, in the horse resembles the keel and cut-water of a boat.

9. Ribs.—In the horse the ribs usually number eighteen on each side. They extend in a series of arches of varying curvature from the dorsal vertebrae above, towards the sternum and sides of the abdomen below. Their shape, in a great measure, determines the conformation or shape of the thorax or chest cavity; they protect its contents, and materially aid in its contraction and expansion. They are continued downward and forward by a small piece of cartilage or gristle, and are just slightly attached to the breast bone or sternum; these are called the false ribs. Note that, starting with the first rib, they get longer until the ninth rib is reached; they then get shorter, the last rib being only a few inches long.

10. Scapula or Shoulder Blade.—The scapula is a flat bone situated on the antero-lateral (front side) surface of the thorax or chest cavity, it is triangular in shape, the base being turned upwards. The inferior or lower extremity articulates with the humerus or shoulder bone.

11. Humerus or Shoulder Bone.—The humerus is a long bone extending from the scapula to the radius and ulna in an oblique direction downwards and backwards. Like all long bones it possesses a shaft and two extremities and two articular surfaces.

12. Radius, or Bone of the Fore-arm.—The radius is a long bone, and occupies a vertical position between the humerus and the carpus.

13. Ulna, or Bone of the Fore-arm.—The ulna is an irregular bone, in form triangular, with the base uppermost, and is placed on the supero-posterior or (upper and back) part of the radius.

14. Carpus, or Knee.—The carpus, knee or wrist, as it is incorrectly termed in quadrupeds, is composed of seven and often of eight small, irregular bones arranged in two rows of three each, one above the other, the seventh being at the back of the three in the upper row, and the eight, when present, in a similar position with respect to the lower row. Their names are as follows: scaphoid, lunar bone, cuneiform bone, trapezium, trapezoid, os magnus, unciform, pisiform, which is not always present.

15. Os Metacarpi Magnus, Metacarpal or Cannon Bone.—The large metacarpal, or cannon bone, is a long, straight bone, placed in a vertical direction. Its superior or upper extremity articulates with the carpus and its inferior or lower extremity articulates with the os suffraginis and the two sesamoids.

16. Ossa Metacarpi Parva, or Splint Bones.—The two small metacarpal, or splint bones, tuberous in form (marked or covered with projections) at the carpus and tapering distally (lower portion), are attached to the large bone, one on each side of its posterior (back) surface, by ligaments in the young animal, and by ossification (union of bone) in most grown up, and in all old animals.

17. Proximal Phalanx, Os Suffraginis, or Large Pastern Bone.—The os suffraginis, or large pastern bone, passes obliquely downwards and forwards, and articulates with the cannon bone above, and the median phalanx or os coronae below. It belongs to the class of long bones.

18. Great Sesamoid Bones.—These bones, two in number, are placed side by side at the postero-inferior (back and lower) part of the metacarpus and postero-superior (back and upper) part of the os suffraginis; they are irregular in shape, their back parts are covered with cartilage, for the passage of the flexor tendons of the digit or the last four bones of the limb. Their superior or upper surface is roughened, and their sides, which are grooved for the reception of the suspensory ligament. (This is called the fetlock joint.)

19. Median Phalanx, Os Coronae, or Small Pastern Bone.—The second phalanx, os coronae, or small pastern bone, has no marrow canal, and belongs to the class of irregular bones. It is inclined, like the os suffraginis, obliquely downwards and forwards, and is partly covered by the hoof. The upper portion of this bone articulates with the os suffraginis and the two sesamoids, the lower part articulates with the os pedis.

20. Distal Phalanx, Os Pedis, or Coffin Bone.—The third, or ungual phalanx, os pedis, or coffin bone, is an irregular bone situated within the hoof, and, when in a healthy state, corresponding somewhat to it in shape, being semilunar in form, with the convexity to the front. This bone is very hard and porous, having many openings for the transmission of arteries and veins. In this bone we notice the wall, the sole, the tendonous surface, the articular surface, and the alae or wings. This bone articulates with os coronae superiorly (upper) and posteriorly it articulates with the os navicular bone.

21. Os Naviculare.—The naviculare, third or small sesamoid, or shuttle bone, is an irregular bone, situated with its long axis transversely, behind and below the os coronae, and behind the os pedis, with both of which it articulates, the articulation of the three forming the so-called coffin joint. The lower surface of this bone is important as it is covered with cartilage, and together form a kind of a pully over which plays the great flexor perforans muscle. The remaining portion of the anterior limb or front leg, will be considered under anatomy of the foot. The navicular bone can be plainly seen on Plate [VII], anatomy of the foot.

22. Femur or Thigh Bone.—The os femoris, femur or thigh bone, the largest, thickest, and strongest bone in the body, belongs to the class of long bones, and is placed in a direction obliquely downwards and forwards, articulating with the cup-shaped cavity in the pelvic or hip bones superiorly (or upper), and with the tibia and patella inferiorly (or below). This bone is roughened for the attachment of the powerful muscles of the hip.

23. Patella, or Stifle Bone.—This, the kneepan or stifle bone, is placed in front of the pully-shaped groove of the femur. It is very compact, its front surface being irregular, round and very much roughened, for ligamentous attachment, and its posterior (or back) surface very smooth to articulate with the groove in the femur, presenting two depressions divided by a ridge, the inner being the larger, and in the fresh state enlarged still more by projecting cartilaginous lip, or elevation. The patella increases the power of the hind leg, and it is this bone that causes stifle joint lameness when it slips out of the groove in which it glides normally.

24. Tibia, or Legbone.—The tibia or leg bone, is a long bone, larger at its upper than its lower end, situated between the femur and the astragalus, slanting downwards and backwards. This bone is three-sided, possessing outer, inner and back surfaces, all of which are wider above than below. This bone gives attachment to the flexor muscles of the hip.

25. Fibula.—This is a long slender bone, little developed in the horse, and is an appendage to the tibia, being attached to the outer side of that bone, and extending from its head to its lower third, to which it is affixed by a ligament; the space between the two bones is called the tibial arch. The fibula gives attachment to the peroneus muscle, the muscle that is supposed to be severely contracted when an animal is affected with string-halt.

26. Tarsus, or Hock Bones.—The tarsus, or hock, corresponding to the ankle-joint of a man, is composed of six irregular compact bones, situated between the lower end of the tibia and the superior or upper extremity of the metatarsus; they are arranged in two series; one consisting of the cuboid and three cuneiform bones, the magnum, medium, and parvum, corresponds to the lower row or carpal bones; the other upper series consists of the astragalus and calcaneum; the first, forming with the bone above the mobile portion of the joint, may be said to correspond to the upper row of carpal bones, while the latter, being the lever bone, corresponds to the trapezium. These bones, like those of the carpus, are thickly covered with cartilage on their articular surfaces, which acts as a protection against concussion. It is these bones that become diseased and united when an animal is affected with bone spavin. The calcaneum bone which forms the prominent part, termed the point of the hock, and corresponds to the heel-bone of man. This bone gives attachment to the calcaneo-cuboid ligament, and it is this ligament that is sprained or ruptured in curb of the hock.

28. Metatarsus, or Os Metatarsi Magnum.—This bone presents the same general appearance as the large metacarpal or cannon bone, from which it differs principally in being about one-sixth longer and flattened from side to side. It is rounded and more prominent in front. This bone articulates above with the tarsus bones, and its lower portion articulates with the os suffraginis.

29. Ossa Metatarsi Parva, or Splint Bones of the Hind Leg.—These also present the same general form as the small metacarpal bones of the front leg; the outer is the longest and largest, and has the largest head, with two surfaces which articulates with the cuboid bone; the inner one has also three articular surfaces, two for small, and one for the middle cuniform bones. The two surfaces on each head articulate with corresponding ones on the large metatarsal bone. The remaining bones of the hind extremity, viz.: the three phalanges, with their three accessory bones, so closely resemble the corresponding bones of the fore extremity, that it seems at first sight difficult to distinguish one from the other; the chief differences being, that the first phalanx of the hind extremity is longer; its upper end larger, and its lower end smaller, than in the fore extremity.

COMPARATIVE OSTEOLOGY.

In this section we shall endeavor to point out where the skeleton of the domesticated animals, other than the horse, differ from the typical skeleton of the latter in any important particular. The following descriptions are therefore in all cases comparisons, where comparison is possible, between the typical skeleton and the skeleton in question.

RUMINANTIA.

(Cud Chewing Animal.)

In this class we take the ox as the animal which represents the best for our purpose, the family of ruminating or cud-chewing animals, as cattle, sheep and goats.

The Skull or Cranium.—In the skull of the ox an important feature is the development of the frontal or forehead bone, which extends from below the eyes to the back of the skull, forming the entire forehead and crest or top, in the middle of which is the forehead tuberosity or knob-like elevation, which is very large in hornless animals. Springing from the sides of the top are two processes, varying in size and shape, but corresponding to the shape of the horns, which they support.

Vertebrae.—The true vertebral column is made up of 26 bones divided into seven cervical or neck-bones, 13 dorsal or back-bones, and six lumbar or loin bones.

Cervical or Neck-Bones.—The bodies of these bones are shorter than those of the horse, but same in number.

Dorsal or Back-Bones.—These bones are longer than in the horse, but have the same general form. It gives attachment to 13 ribs on each side in the same manner as those of the horse.

Lumbar or Loin Bones.—The lumbar vertebrae are longer and thicker than in the horse, their bodies being more round on the sides and lower surfaces.

Sacrum, or Rump Bones.—The sacrum is larger and more arched, and the upper surface more round than in the horse.

Coccygeal or Tail Bones.—The tail bones are from 15 to 20 in number, are strong and rougher than those of the horse.

Pelvis or Hip Bones.—The pelvis is larger, but presents the same general appearance as in the horse.

In studying the bones of the limbs in ruminants, the only point of difference is in bones below the knee. The large metacarpal bone presents a vertical groove down its front, which marks the original division of the bone into two bones. The lower extremity is divided by a deep groove into two articulations, each resembling the single one of the horse. The outer one being always the smaller, a rudimentary metacarpus is placed on the back and outer surface. The pasterns and sesamoids in either limb are double, one set forming each digit; they are small and narrow, the coffin bone resembles half of that of the horse, equally divided.

In the aged ruminant, two bones are commonly found in the heart, and may be termed the cardiac bones. They are found related with auriculo-ventricular rings. In shape they present three angles, three borders, and two surfaces. The left bone is somewhat smaller than the right.

OMNIVORA.

Animals eating both vegetable and animal food.

The omnivora are represented in veterinary anatomy by the hog.

CARNIVORA.

An order, suborder, or family of mammals, especially wild animals, including the dog and cat, etc. Animals that eat flesh.

In this order our description alludes mostly to the dog.

AVES.

The scope of the present work will allow only very brief treatment of this part of the subject.

Of or pertaining to Birds, Poultry, Etc.

The bone tissue or substance of birds are exceedingly compact and hard, white in color; and some of the bones are pneumatic, or contain air instead of marrow, notably these are bones of the skull, the sternum or breast bone, and the upper bones of the limbs. There are a great variety in the amount of pneumaticity or air possessed by the skeleton of different species, but it is not necessarily determined by the flying power of the animal.

CHAPTER II.

ARTHROLOGY.

What is known regarding the articulations of bones of joints. The several bones which form the skeleton are united by means of certain soft structures, forming a number of articulations or joints, the study of which is termed arthrology.

Before considering the different forms of joints, it will be advisable to describe briefly the various tissue, other than bone, which enter into and contributes towards their formation. These are chiefly cartilage, connective and elastic substance or tissues, and fat.

In health, one bone never comes directly in contact with another, cartilage or fibrous tissue being always interposed; an exception to this exists in the adult skull, most of the bones of which become firmly united by ossification of the interposed soft material.

Cartilage.—Cartilage, known also by the familiar name of gristle, is a firm, bluish-white elastic animal substance, somewhat transparent, resilient, and flexible, possessing great cohesive power. That which forms the original basis of the bony framework is termed temporary, and that which persists in the adult, permanent cartilage; the former disappears as it is replaced by bone, but the latter, of which alone we have to treat here, never under normal circumstances become ossified. Cartilage consists of corpuscles or cells, usually embedded in an intercellular substance.

The articular cartilage is important as it encrusts the articular surfaces of bones, helping to form joints by supplying smooth, elastic cushions, which diminishes both concussion and friction.

Connective Tissue (White fibrous tissue.)—In one form or another this tissue is found in all parts of the body. The chief varieties are the areolar and the fibrous; the former serving as a connecting medium, and support to the various organs, and to the structures of which they are formed. It appears as a loose, transparent mesh, its interwoven bundles forming spaces termed the areolar or cells.

Connective tissue contains nerves and blood-vessels, for the supply of neighboring structures as well as for its own nourishment. When healthy it is little sensitive to pain.

Yellow Elastic Tissue.—This differs from the white or connective tissue in being yellow, elastic, and not so tough or strong. Its fibers are usually large but when mixed with the white tissue in tendons the size diminishes.

Yellow elastic tissue is found nearly pure in the ligamentum nuchae, and tunica abdominis, the coats of the largest arteries and elsewhere. The lungs contain a large quantity of this tissue.

When white fibrous tissue is boiled gelatine is obtained, which is not the result of boiling the yellow elastic tissue.

Adipose Tissue.—Fat or adipose tissue consists of cells containing an oily material, and arranged in isolated groups, or slightly separated by meshes of areolar tissue. It is found in many parts of the body, and varies greatly in quantity; in joints it occurs between the ligaments, and serves the purpose of a packing material, while in the form of medulla or marrow it occupies the cavities of bones. In fat cell a nucleus is very rarely visible.

Ligaments.—Ligaments are dense, fibrous, connecting structures. They exist in most articulations, and are made up principally of white fibrous tissue. There are two kinds—capsular or bursal, and funicular or binding ligaments.

Capsular ligaments are membranous structures enclosing true joints. They consist of a dense interlacement of fibers attached to bones, round the edges of the articular cartilages; some regard them as a continuation of the periosteum or the covering of bone. They are never closely applied, their use being to form cavities round the joints, enclosing and protecting the synovial or lubricating apparatus inside.

Funicular or binding ligaments consist of rounded or flattened cords, or bands of fibrous tissue, passing from one bone to another, firmly attached to roughened portions of their surfaces. They hold the bones in their places, at the same time allowing the requisite amount of motion in the joints. Ligaments which are situated between bones are often termed interosseous. Annular ligaments are those which bind down and protect the tendons of muscles in certain joints, converting grooves in the bones into channels or tubes which are lined with synovial membrane, and through which the tendons play.

Some ligaments are composed almost entirely of yellow elastic tissue, such as the ligamentum nuchae (the elastic ligament of the neck) and the ligaments connecting the vertebral arches (arches between the bones of the spinal column).

Synovial Membranes.—These are thin membranes lining the capsular ligaments of joints, or they are interposed elsewhere between structures which move one upon another, and which would otherwise be injured by the friction. Near the borders of articular cartilages the membrane is generally found as a projecting fold, the projection being due to a small pad of fat, interposed between the membrane and the capsular ligament. These projections were once erroneously termed synovial glands, but their use is probably to assist in forcing the synovia between the opposing surfaces of cartilage.

Synovia.—Synovia or joint oil, is a viscid, transparent fluid, colorless, or pale yellow, physically resembling oil, but it contains very little fatty material, consisting chiefly of albumen, salts and water; it is secreted by the cells of the inner surface of the synovial membrane. When an animal is in active exertion, there is a greater demand for joint oil than when at rest, consequently there is an increased secretion of it.

Classes of Joints.—Joints may be divided into three classes—Immovable, movable and mixed.

Motion in Joints.—The following terms express the various movements allowed by joints—Extension tends to bring two bones as nearly into a straight line as the structure of the joint will permit; flexion is the reverse of this, and diminishes the angle that extension increases; abduction expresses the outward movement of a limb or bone from the central line of the body; adduction is the reverse action; rotation signifies the partial revolution of a bone or number of bones, as it were, on their own axis; circumduction implies the movement of the lower end of a bone or limb, where it describes a curve, as the bow of a circle, ellipse, etc. The term gliding explains itself, and is peculiar to movable and other joints having no frictional surfaces.

Important points of joints to be considered will be described on Plate [I] by Roman figures to correspond with those given below.

Joints of the Front Leg.

I. Shoulder Joint.—This joint is formed by the lower end of the scapula, or shoulder blade, and the upper end of humerus or shoulder bone. This is a ball-and-socket joint, and is held in its place by ligaments and muscles. This belongs to the class of rotation joints, its action is outward, inward, backward and forward.

II. Elbow Joint.—This joint is formed by the lower part of the humerus and the upper portion of the radius and ulna. It is covered with ligaments and muscles similar to the above mentioned joint. This is a hinge joint the action of which is only forward and backward, or flexion and extension. It has no lateral movement.

III. Carpus or Knee Joint.—This joint has been explained very thoroughly in the previous chapter. There are three separate articular surfaces in this joint. This joint has a large capsular ligament, and has binding ligaments one above the other, the seventh being at the back of the three in the upper row, and the eight, when present, in a similar position with respect to the lower row. Thus there are three separate articular surfaces in this joint. The upper surface of the carpus articulates with the radius; this forms the hinge joint of the knee and is where flexion and extension takes place. Another articulation between the upper and lower carpus bones give slight motion to the knee, but not so much as the upper articular surface. Between the lower surface of the lower row of carpus bones and the upper extremity of the metacarpal, or cannon bones, is another articular surface which gives motion to the knee. This joint has a large capsular ligament, and has binding ligaments inside and outside. In addition to the flexion and extension movement the knee joint possesses, it also serves as a cushion and relieves concussion of the fore limb.

IV. Fetlock Joint.—This joint is formed above by the lower portion of the metacarpal, or cannon bone, and below by the part of the os suffraginis or the large pastern bone. At the back of this joint there are two small bones called the sesamoid bones. This joint has a capsular and two lateral binding ligaments. The motion of this joint is a backward and forward or flexion and extension, same as that of the knee.

V. Pastern Joint.—This joint is situated just above the hoof, and is formed by the lower end of the os suffraginis or large pastern bone and the upper end of the os coronae or small pastern bone. It has a capsular and lateral binding ligaments, same as the fetlock joint. It also has the same motion as the fetlock joint, and is often the seat of what is termed a high ringbone.

VI. Coffin Joint.—This joint is situated within the hoof. It is formed above by the lower end of the os coronae or small pastern bone, and below by the upper surface of the os pedis or coffin bone. Immediately behind this joint, and articulating with the two mentioned bones, is the navicular, or shuttle bone—it gets its name from its likeness to the shuttle of a sewing machine. This bone when diseased is the seat of navicular disease, or coffin-joint lameness. The action of this joint is very slight forward and backward.

Joints of the Hind Leg.

VII. Hip Joint. The hip joint is formed by the pelvis and femur bone. This is a true ball-and-socket joint similar to the shoulder joint. It has a capsular, and is called the round ligament, in the joint, holding the head or ball on the femur in the socket of the pelvis. This can be seen plainly by examining the joint. This round ligament is important, as it often becomes strained, being the seat of hip joint lameness. It is also held together by the strong muscles of the hip. Its motion is rotation similar to that of the shoulder joint.

VIII. Stifle Joint.—This joint is formed above by the lower end of the femur, or hip bone, and the upper end of the tibia or thigh bone. These two bones in front form a pulley-like surface on which the patella, or stifle bone, is situated. This bone, when the joint is in motion, glides up and down over the pulley-like surface. It sometimes becomes displaced, and this is termed dislocation of the patella or stifle bone. This is an important point to notice about this joint. It has a capsular and lateral, or binding ligament, which hold the stifle bone to its place as it plays upon the pulley-like process of this joint. The action of this joint is only forward and backward or flexion and extension. It has no lateral or side motion.

IX. Tarsus or Hock Joint.—This joint contains six bones. The two upper bones, one of which is a pulley-like bone placed in front, and the other placed behind, forms that portion of the hock which is called the point of the hock to which the muscles of the gambe are attached. It can be easily seen or felt. The upper surface of these two bones articulate with the lower portion of the tibia or thigh bone, and forms a true articulation of the hock joint. This part is what gives most of the motion to the joint. Below these are three other small, irregular bones, placed one upon the other, having an articular surface between them. Immediately behind these three small bones is what is called the cuboid bone. This bone also articulates with the three small irregular bones, helping to form the articular surface of the hock. The lower articular surface helps to give a small amount of motion to the joint. This joint is the seat of bone or bog spavin due to severe sprains, or poorly conformed joints.

Fetlock, pastern and coffin joints of the hind leg are so closely allied to those of the fore leg that it is not worth while discriminating between them.

CHAPTER III.

MYOLOGY.

The branch of anatomy which treats of the muscular system is called Myology.

Muscles are the active organs of motion, or locomotion, each being separated from the other by a thin delicate membrane made up of connective tissue, which forms a sheath for the muscle. A muscle is divided into two parts, viz.: muscular and tendinous. The muscular part is the larger of the two. It is sometimes called the belly of the muscle or flesh. This part is known as muscular tissue, and has a reddish, meaty color. At both ends of the muscle there is a tendinous part, or the hard, white portion of the muscle which becomes attached to the bone. All muscles are attached to two or more places of different bones, and when contracted, the joints of the body are moved. They are well supplied with nerves, which give strength and feeling, and also well supplied with small blood vessels, from which the muscle is fed. Muscles are found in separate groups, all of which have different actions to perform. There are two kinds of muscles—voluntary and involuntary. The voluntary muscles are under the control of the will of the animal; example—the muscles of the head, neck, back, hip and legs. The involuntary muscles are beyond control of the animal, and will act even though the animal were asleep—such as those of the heart, the large muscular curtain which separates the chest cavity from the abdominal cavity, which is one of the great muscles of breathing; also the muscles around the chest which assist in breathing.

MUSCLES OF THE HORSE—SUPERFICIAL LAYER—AFTER MEGNIN.

EXPLANATION OF PLATE II.

Muscles of the Horse.

This illustration shows the superficial muscles of the body after the skin and panniculus carnosis muscle has been carefully removed. This muscle is spread over the greater part of the body, which is related externally with the skin; internally with the superficial layer of muscles. Its action corrugates the skin, and thus enables the animal to expel or shake off insects and irritating bodies, its use being thus protective to some extent; it also supports and binds down the superficial muscles.

SUPERFICIAL LAYER.

The panniculus and tunica abdominalis are removed.

Voluntary Muscles.—The voluntary muscles are in groups. The first muscle we will call the student’s attention to, after removing the skin, is the panniculus carnosus (not shown in Plate [I]), which is a thin muscle, and almost entirely covering the body, which is sometimes accidentally removed by a careless person in skinning the animal. The action of this muscle is to shake the skin when flies or other objects bother the horse. This muscle is not shown in Plate [I] it having been removed in order to show the more important ones.

Head Muscles.—At the head there is a group of muscles which assist in chewing, or masticating, the food.

Gullet or Pharynx Muscles.—Around the throat is another set of muscles, sometimes called the muscles of the gullet, or pharynx, which assist in swallowing.

Neck Muscles.—The neck muscles are divided into two groups, one on each side. The action of these is to raise and lower the head, also to turn the neck and head from side to side.

Muscles of the Back.—The muscles of the back are generally divided into two groups, one above the spinal column and the other below. The muscles above the spine assist the animal in running, jumping and rearing. The muscles below the spine are sometimes called the psoae, or lumbar, muscles, situated below the lumbar bones, or the bones of the small of the back. The action of these muscles is to assist the animal in getting up. These muscles are important, for when paralyzed the horse cannot use his hindquarters. Below these muscles are the kidneys.

Hip or Gluteal Muscles.—The muscles of the hip are very large, filling in around the hip bones. The action of these is much the same as those of the back, as they assist in jumping, running, rearing and in flexing and extending the hind leg.

MUSCLES OF THE HORSE—DEEP LAYER—AFTER MEGNIN.

EXPLANATION OF PLATE III.

Muscles of the Horse.

Deep Layer.

Tail or Coccygeal Muscles.—Here there are four that are important, one situated on the upper side of the tail when straight out, the action of which is to raise the tail; two, one on each side of the tail, have the power of drawing the tail to either side; the fourth is situated under the tail and is the smallest one of the four. Its action is to draw the tail down.

Abdominal Muscles.—The abdominal or belly muscles, are four large, flat muscles on each side of the abdomen. The outer edge of these muscles is attached to the outer ends of the false ribs, also to the processes of the lumbar bones and the outer angles of the pelvic or hip bones. They unite below to what is called the linea alba, a hard, white fibrous cord. They pass back in the center of the belly and are attached to the front of the pelvic bones, called the lower bones of the pelvic cavity. About ten inches from where it is attached here, passing forward, is a small slit or hole, which is called the navel, or umbilical opening. Here the navel vessels pass in and out during the foetus life, or before the colt is foaled. This is a point of importance to note, for sometimes at the time of birth this opening does not close and allows the bowels to come down and form what is known as umbilical or navel rupture.

Before finishing the description of this group of muscles a very large, important ligament should be noted, which is found spread all over the abdomen of the horse. It is of a yellowish color and about one-eighth of an inch thick, attached in front to the back of the breast bone and to the pelvic bones behind. This is the first structure seen after removing the skin from the abdomen. This ligament gives great support to the organs contained in the abdominal cavity. The action, or uses, of the abdominal muscles are to support the organs contained in the abdominal cavity, to flex the back-bone and assist in passing of the feces. In the mare these muscles assist in parturition, or foaling.

Shoulder Muscles.—The shoulder muscles are very large and powerful. There are only three of great importance. Two situated on the outside of the scapula or shoulder blade are important, as they are muscles affected in the disease called shoulder sweeny. The other important one is that which passes down over the shoulder joint through the groove or pulley-like surface on the humerus, or shoulder bone. This is a long, powerful muscle, attached above to the lower end of the scapula, or shoulder blade, passing down through the groove mentioned, and is attached to the upper and front part of the radius or fore arm bone. Its chief point of importance rests in its action in raising the front leg, where it passes over the pulley-like surface mentioned, when it becomes injured or diseased; it is the seat of shoulder joint lameness.

Muscles of the Front Leg.—Muscles of the front leg, from the shoulder down, are divided into two separate kinds, the extensor and flexor muscles. The extensor muscles are those which bring the leg forward. These muscles above are attached to the bones around the elbow joint, passing down in front of the arm bones. About three inches above the knee they become changed into the tendinous part of the muscles, or what is called the cords of the leg. Some of them are attached to the bones about the knee joint, while others pass over the front of the joint and are held down to their place by a band or ligament, forming a loop, as it were, for the tendinous portion of the muscle to glide into when the leg is in action. Each one of these loops through which the muscles pass are supplied with a synovial membrane to secrete the synovia, or oil, which lubricate it during action, the same as in the joint. This is a point of importance, as sometimes, on account of injury or strain of this part of the joint through which the muscles play there may be found a small, puffy enlargement containing oil secreted by the synovial membrane. This disease is called bursal enlargement.

The flexor muscles are situated at the back part of the leg, attached above to the back part of the elbow joint, passing downwards at the back part of the leg. About two or three inches above the back part of the knee joint they become tendinous, and from there down to the back part of the coffin bone, where two of the principle muscles are attached; these form what is known as the back tendons, or cords, of the leg. Some of them become attached to the back part of the knee, same as the muscles on the front part of the leg, while the other two principal tendons pass through a loop formed by ligaments, the same as those mentioned in the front part of the knee. In tracing these tendons down from the knee to the fetlock, notice that they pass through another larger loop or sheath formed at the back of the fetlock, where some of the fibers are attached, while others continue down at the back part of the pastern bones, and are attached to the os pedis or coffin bone. These tendons are important, because when they are strained the fact is spoken of as the strain of the back tendons. The action of these muscles is to flex the leg, bend the knee, pastern joints and fetlock.

Muscles of the Hind Leg.—These are also divided into two groups, extensor and flexor. The extensor muscles are situated in front of the hind leg. They are attached above, around the stifle joint, and pass downward in front of the tibia, or thigh bone, one being attached to the front part of the hock. The other passes through sheaths, or loops, supplied by a synovial membrane, formed by ligaments, to hold the muscles firm in front while the leg is in action. In tracing them down, in front of the shin bone to the fetlock, note that they pass through loops, or sheaths, and continue down in front of the pastern bones to where they are attached. The action of these is to bring the leg forward.

The flexor muscles of the hind legs are attached, above, around the back part of the stifle joint. In tracing them down it will be found that they become tendonous. Two of the principal ones pass down to that part of the hock joint, which forms the point known as the cap. These form what is called the gambe of the leg, and are partly attached at the point of the hock, and other part passing down to the fetlock joint through a loop, or sheath, along the back part of the pastern bones, and are attached to the os pedis or coffin bone of the foot. This muscle, from the hock down, forms one of the back tendons of the hind leg. Another important muscle is found passing down underneath those already mentioned, through a loop, or sheath, at the back part of the hock, where it is supplied with a synovia sac. This is a point of importance, because when it becomes sprained it is the seat of what is called thoroughpin. It then passes down the back part of the shin bone beneath the other tendons already mentioned, through the loop at the fetlock to the back part of the os pedis or coffin bone, where it is attached. The action of these muscles are to flex or bend the fetlock and raise the hock joint in traveling.

Involuntary Muscles.—Involuntary muscles, or muscles not under the control of the will. The first to notice are those of breathing or respiration. They form a group situated about the chest in such a way as to be the means of increasing or decreasing the size of the chest cavity. When these muscles expand the chest cavity is enlarged, causing the air to rush into the lungs, known an inspiration. On the other hand, when these muscles contract the air is expelled from the lungs, known as expiration.

The diaphragm is a muscular curtain which separates the chest from the abdominal cavity. It also assists greatly in drawing the air in, when it contracts. This muscle also assists in passing faeces, and in the mare foaling. It separates the heart and lungs from the bowels, liver and stomach. This muscle should be carefully examined by the students. It can be seen by opening any dead animal.

There is one muscle which is both voluntary and involuntary. It is situated in the penis, surrounding the urethra, or the tube, which carries the urine from the bladder to the penis in the male animal. Its action is voluntary while the animal is passing urine. It is involuntary during sexual intercourse, forcing the semen down through the penis.

DIGESTIVE AND MALE URINARY APPARATUS OF A HORSE—AFTER MEGNIN.

EXPLANATION OF PLATE IV

Digestive Apparatus of the Horse

CHAPTER IV.

SPLANCHNOLOGY.

Study of large interior organs in any of the four great bodily cavities especially those in the abdomen.

Digestive Organs of the Horse.—The digestive organs comprise the alimentary canal and the accessories by which the alimentary matter is received and subjected to specific actions, which adapt it for purposes of nutrition. Digestion, therefore, embraces the collective operations and changes which the food undergoes in the alimentary canal.

The whole digestive track from the mouth to the anus which is situated just below the tail, is sometimes called the alimentary canal.

The mouth is an oval cavity at the commencement of the alimentary or digestive canal. In front of the mouth are the lips, one above and one below; at the sides are the cheeks. The mouth is lined with what is known as the mucous membrane, in which are several small openings, from the glands, which are situated about the mouth. Through these the saliva is poured. On the upper part of the mouth the mucous membrane is thrown into ridges, or folds, from 18 to 20 in number. This is a point of importance in connection with bleeding a horse with lampas. It is never safe to bleed back of the third bar because there is a large artery which runs down through the roof of the mouth and enters the hole in the bone just before it reaches this bar. The tongue, which has the chief nerves of the sense of taste, is situated in the mouth; this organ also has a very important part to perform in masticating the food and mixing it with saliva. The teeth, which also take a very active part in the masticating of food, are dealt with under the heading of “Teeth.”

Salivary Glands.—These glands secrete the saliva that is poured into the mouth while the animal is eating. There are only three pairs of much importance. One large pair, one on each side of the throat below the ears, known as the parotid glands, fill up the space between the jaw bone and the neck. This pair has tubes passing around and under the lower jaw and up into the cheek muscles entering the mouth opposite the fourth molar tooth. These tubes, known as steno’s ducts are about an eighth of an inch in diameter and convey the saliva from the glands into the mouth. The next pair are situated under the pair just mentioned. Their tubes enter into the bottom part of the mouth. The third pair are situated under the tongue, one on each side. They pour their secretion into the mouth by several small openings near the front under the tongue. This can be seen by examining the under surface of the tongue closely. This is very important fluid in connection with the digesting of the food.

The gullet is a cavity situated just back of the mouth. It is chiefly made up of muscles which perform the act of swallowing the food. It is lined with the continuation of the mucous membrane of the mouth.

The oesophagus, or the continuation of the gullet, is a tube extending from the gullet to the stomach, and is used to convey the food to that organ. It is made up of two coats, the muscular and the mucous. The former contains fibers which, when once the food enters the tube, contract behind it, forcing it down to the stomach. Its lining is a continuation of the mucous membrane of the mouth and the gullet. In tracing the oesophagus or tube down the neck from the gullet, note that it passes down the left side of the neck, entering the thoracic, or chest cavity, between the lungs over the heart through the large muscular curtain known as the diaphragm, then enters the stomach an inch or two after passing the diaphragm.

The Stomach.—This organ is very small in the horse in comparison with that of the ox. It holds only about four gallons, and is situated just back of the curtain which separates it from the lungs. It lies mostly to the left side. The walls of the stomach being composed of three coats. That on the outside is called the serous membrane, a name applied to membranes which line closed cavities, such as the abdominal cavity. The inside lining is a continuation of the mucous membrane lining the organs before mentioned. The lining in the left part of the stomach or the part where the food is prepared for digestion is the same color as that of the mouth. The lining of the right part of the stomach, which is the true digestive part, is of a deep red color resembling velvet, and when placed under a microscope has the appearance of a honey-comb. When the stomach is empty this membrane is thrown into loose folds. Several small openings may be noticed through which the gastric juice and pepsin from the glands, situated in the walls of the stomach, enters. These are very important fluids as they assist greatly in digesting the food. The third coat is known as the muscular coat already mentioned. Its action is to give the stomach a churning motion, rolling the food around and mixing it with the juices. The opening to the stomach is guarded by a valve which prevents the food from passing back through the gullet. There is also a valve at the opening of the bowels, preventing any coarse, undigested food from entering them. The stomach is held in its place by five large ligaments, and is well supplied by blood-vessels and nerves. Digestion of the food takes place very quickly in the horse in comparison to other animals. Frequently a change of food or working too soon after eating will interfere with the digestion, thus setting up what is known as indigestion. This is a very painful disease in the horse. After the food is acted upon by the juices in the stomach it changes into what is known as chyme, which passes into the bowels.

The Bowels.—They are divided into two parts—the large and small.

The small bowels are 72 feet in length, about one inch in diameter, and are made up of three coats, same as the stomach. The serous coat on the outside contains small glands which secrete an oily material to lubricate the outside of the bowels, which comes in contact with the inner wall of the abdominal cavity. The muscular coat, made up of muscular fibers, is situated between the other two coats, the same as in the stomach; its action is to contract the bowels, giving them motion to convey the food along through them. The mucous coat is a continuation of the mucous coat of the stomach. Along this coat are found small glands known as villi lacteal; these absorb the nourishment from the food as it passes along through the bowels and pours it into the blood. The small intestines or bowels are attached on the upper side to what is known as the mesentery, which is attached above to the roof of the abdominal cavity. It can be seen in any of the smaller animals upon examination. About six inches from the stomach, in the bowels, are found two openings. One of these receive the hepatic duct, a tube for the purpose of carrying the bile from the liver to be poured in on the food as it passes through the bowels. The other opening is for the duct of the gland known as the pancreas. It secretes a clear fluid known as the pancreatic juice. These juices act on the food in the first part of the small intestines, changing it into chyle. After this, the action of the rest of the intestines is to absorb the nourishment out of the food as it is passing back. The small intestines and stomach, when in a healthy condition, should be found empty one hour after food has been eaten. The small bowels or intestines are situated mostly on the left side just behind the stomach.

The large bowels have three coats, the same as the small ones. The first part of the large bowels is known as the blind bowel or caecum, and is about three feet in length; this is generally the first thing to protrude when opening a horse’s abdominal cavity. Its use is to act as a reservoir to hold the water and fluid of the food; from this organ the water and fluid parts are mostly taken up into the system. The next part of the large bowels is known as the large colon; it lays along the floor of the abdominal cavity, is about nine feet in length and is doubled on itself three times. In this bowel the solid part of the food is found. Here digestion is brought about by the contraction and expansion of the muscles of the bowel and the nourishment taken from it, after which it is worked back out of this bowel and enters what is known as the floating colon. This is about ten feet in length and about two inches in diameter, or double the size of the small bowel. It is thrown into folds or pleats, and as that portion of the food containing no nourishment passes through it is worked into balls which pass back and are emptied into the rectum or back bowel. This is situated at the back part of the abdominal and pelvic cavity back of the small bowels or intestines and like them, is suspended by a fold paritoneum.

The rectum or back bowel is sometimes known as the straight bowel. It is about 18 inches long and forms the last part of the bowels or intestines. Its coats are a continuation of those of the large bowel, but each is thicker and heavier. Above this bowel are the bones of the sacrum, below it, in the horse the bladder and other small glands. Below the rectum of the mare are situated the womb and the vagina, the latter being the passage into the womb from the outside. The bones which help to form the pelvic cavity are situated at the sides, and at the back immediately under the tail is what is known as the annus. The use of the rectum is to hold the balls as they pass back from the floating colon. When the rectum becomes so full that there is pressure on the sides of the wall thus stimulating the nerves the muscular coat contracts and forces the contents back towards the annus. At the same time the muscles of the annus dilate, causing the faeces to pass out.

Accessory Organs of Digestion.—In the abdominal region these organs are the Liver, the Pancreas, and the Spleen.

The Liver is the largest gland in the body and is situated between the stomach and the diaphragm. The liver of the horse weighs from ten to twelve pounds. It is of a dark brown color, well supplied with blood and nerves, and is held in place by several strong ligaments. A bitter, greenish colored fluid called the bile is secreted from the liver and emptied into the digestive system, where it plays an important part in its action on the food. There is no gall bladder in the horse, but simply a tube passing from the liver to the small bowel into which it empties the bile about six inches back of the stomach. It is important to note that it is in this tube that gall stones sometimes collect.

The Pancreas is another very important gland. It is of a grayish, fatty color, and may be found near the roof of the abdominal cavity in front of the kidneys. The Pancreas secretes a clear, colorless fluid called the pancreatic juice. This fluid, like the bile from the liver, also plays an important part in the digestion of food. It is carried down from the Pancreas by a duct or tube emptying into the small bowel just back of that of the liver.

The Spleen is a long, flat gland about fifteen inches in length, situated along the left side of the stomach and to which it is closely attached. It is of a grayish red color and feels quite soft. It is ductless, there being no secretion passing from it. The function of this gland is not clearly understood, but by many it is supposed to regulate the temperature of the stomach during the process of digestion and to act as a reservoir for the blood. Some speak of it as the burying ground of the red corpuscles. It is well supplied with blood vessels and nerves and weighs about two pounds in an average sized horse.

RUMINANTIA.

Digestive System.—The lips of an ox are thick and hard. The upper has no hair on it and varies in color with the color of the animal. When cattle are in good health this space is always moist.

The cheeks on the inside are covered by many small rough processes, which give them a very rough appearance.

The Tongue of the ox is stronger than that of the horse and is more movable. It is very thick and heavy at the back, pointed at the front end and the upper part of it is very rough. It is by means of the tongue that the ox takes most of the food into the mouth.

The Salivary glands are similar to those of the horse.

The Teeth differ very much from those of the horse.

The ox has no front teeth in the upper part of his mouth, their place being taken by a pad of cartilage or gristle. This pad takes the place of the upper row of front teeth. The lower row of teeth press against it when the animal is cropping grass. This accounts for the fact that cattle do not do as well on short grass as horses.

The front teeth in the lower jaw also differ from those of the horse. They are eight in number, chisel-shaped, and are loosely set in the gum.

The molars, or back teeth, are similar to those of the horse, only they are smaller and not so smooth on their upper surface. The ox has twenty-four molars or back teeth, and eight incisors or front teeth, making thirty-two in all.

The Gullet of the ox is much larger than that of the horse.

The Oesophagus or tube, which carries the food down from the mouth to the stomach is well developed, the fibers in it being very strong and possessing a double action. When the animal is eating they carry the food from the mouth to the stomach, and when chewing the cud they act the very opposite, carrying the food from the stomach back into the mouth.

The Stomach.—The student will do well to give some time to the study of this important organ of the ox, as it is very frequently the seat of disease.

The stomach has a capacity of fifty-two gallons and is divided into four separate and distinct compartments: the Rumen or Paunch, the Reticulum or Honey Comb, the Omasum or Many-plies, and the Abomasum or the true Stomach. In the first three of these the food undergoes a sort of preparatory process, while in the fourth the process of digestion is complete.

The Rumen or paunch is very large, and in an aged animal fills three-quarters of the abdominal cavity. It lies up against the left side of the wall of the abdomen, where it is attached and held to its place by the ligaments. Its situation being an important matter, as many diseases of the rumen, or paunch, are first noticed on the left side. Tapping for bloating is always done on the left side because of this fact. The walls of the paunch of an ox resemble those of the stomach of the horse, but are not so sensitive, and stand a great deal of abuse before inflammation sets in. The paunch has two openings, both of which are at the front; through one the food enters, while through the other it passes out into the next division.

The Reticulum, or honey comb, is the smallest division and resembles a honey comb in appearance. This part has little to do with preparing the food. It is provided with two openings, one in front, where the food enters, the other at the back, where it passes through into the third division. In the reticulum, or honey comb, the food is softened further by the water that the animal drinks which passes directly into the second division. The food is here pressed into balls and prepared to be forced back into the mouth to be further masticated.

The Omasum, or many-plies, is the second largest division of the stomach. When full it is ovoid in shape. It is placed just behind the second division and at the right side of the paunch. The inside is full of folds, or layers of membrane, into which all the coarse parts of the food pass and roll about until it is fine and well prepared to pass into the last division. When this part of the stomach becomes deranged and the food becomes dry and hard between the folds, the disease called impaction of the many-plies, or dry murrain, is the result.

The Abomasum, or fourth stomach, is the true digestive part. In it the food is completely digested. The walls are redder in color than those of the three first divisions and contain the glands which secrete the acids and gastric juices. This stomach has two openings, one through which the food enters and the other through which it passes into the small bowels.

The Bowels, or intestines, of the ox are divided into large and small bowels. This, together with their structure and action resembles that of the horse. The small bowels are only half the size of the horse, being about one-half inch in diameter, and about one hundred and fifty feet in length. The large bowels are not nearly so long as those of the horse and are thirty-five feet in length.

The Liver of the ox resembles that of the horse, except that it is provided with a gall bladder which resembles a pear in shape. This acts as a sac in which to store the gall during the time it is not required in digestion. When digestion is going on the wall of the gall sac contracts and forces the gall down to the food. The other glands, the pancreas and spleen, resemble those of the horse. The juices from these glands have the same action in cattle as they have in the horse.

Rumination, or Chewing the Cud.—Food when first taken into the mouth of a ruminant is but lightly masticated and mixed with the saliva from the salivary glands, after which it is swallowed, passing through the oesophagus into the rumen or paunch (first stomach). This division acts as a reservoir or storehouse for food thus eaten quickly. When the animal has time, so to speak, he lies down or stands quietly and completes the process of mastication of his food by chewing the cud. This peculiar act is performed as follows: After being softened and moistened by warmth, the food passes from the rumen or paunch into the second division—the reticulum, honey comb or second stomach. In this small globe-like compartment the food is moistened and compressed into pellets—the cud. By a peculiar reverse action of the oesophagus or gullet these pellets are taken back into the mouth for further mastication or chewing. When re-mastication is completed it is again swallowed, but this time it passes directly into the omasum, many-plies or third stomach, and thence to the fourth or true stomach.

Process of Digestion After Rumination.—Following rumination which, strictly speaking, is the first step in the digesting process, the food passes into the third stomach. The fine parts pass right along to the fourth stomach while the coarser parts are drawn between the folds of the membrane in this division and worked about until it is fine and ready to pass into the fourth stomach, where it becomes fully digested by the action of acids and gastric juices which are secreted in this part. It then passes into the small bowels, and is acted upon by the bile from the liver and the pancreatic juice from the pancreas. These juices are emptied into the first part of the small bowels through little ducts or tubes, which lead from the glands down to the bowels, just on the same principle as that of the horse. After this, throughout the rest of the bowels, the nourishment of the food is taken into the system by means of little glands which are situated in the coating of the bowels. The nourishment when once in the blood goes to supply the different parts of the body, while the part containing no nourishment or undigested passes off through the back bowels in the form of feces.

TEETH.

Teeth are objects situated in the upper and lower jaws. They are made of the same tissues as bone but contain 10¹⁄₂ per cent. more of earthy salts. This fact accounts for their extreme hardness. Unlike bone they can stand exposure to air and friction without becoming diseased. Teeth are used to masticate or chew the food, and because of the constant change in their formation and appearance they serve as a guide in telling the age of the horse.

There are three hard structures that enter into the formation of the teeth—Dentine or Ivory, Enamel, and Cementum, or Crusta Petrosa.

The Dentine, or ivory, is situated in the upper part around the pulp or nerve cavity. It is of yellowish color and largely supplied with nerves which pass through it from the pulp cavity.

The Enamel is the hardest substance of the tooth, and covers the outside of all the exposed part. This substance is characterized by its whiteness and, unlike the dentine, contains no blood vessels or nerves. If part of the enamel is broken off it is never replaced, and the tooth below the broken part generally becomes decayed.

The Cementum, or crusta petrosa, is found in the fang or root and the parts situated below the gum. It is the softest part of the tooth.

Teeth may be simple or compound. Simple as in the dog, where the entire exposed surface is covered by a solid cap of enamel, which alone is in wear; compound or complex, as in the horse, where various tissues are in wear. A tooth consists of the following anatomical parts: The body, or crown, that part above the gum; the table, the part that comes into wear on the top; the neck, the part to which the gums are attached; and the fangs or roots, the parts situated down in the bone.

There are three kinds of teeth found in the horse, the incisors, the canine and the molars.

The Incisors, or front teeth, situated in the front part of the mouth just inside the lips, are twelve in number, six above and six below.

The Canine, or bridle teeth, are often absent in the mare. They are four in number, two in the upper and two in the lower jaw, one on each side about two inches back from the incisor teeth. They are from a quarter to three-quarters of an inch above the gum, are round and pointed and of no particular use. They resemble the eye teeth of other animals.

The Molars, or back teeth, are twenty-four in number, six on each side in the upper and six on each side in the lower jaw. With these the food is ground and masticated.

Wolf Teeth are two small, round, pointed temporary teeth which vary in size in different animals, situated one on each side in front of the molars or back teeth in the upper jaw.

Temporary and Permanent Teeth.—The horse has two sets of teeth. The milk are temporary and are those that the colt sheds; while those that come in and remain without being shed are called the permanent teeth. The cutting of the teeth of the foal varies, but at or within nine days after birth he has four front teeth, two in the center above and two below, and in the back part of the mouth twelve molars. At from seven to nine weeks four more incisors or front teeth appear, one at each side of the two center teeth in each jaw. At nine months he gets the last of his milk or temporary teeth, these being the corner teeth, two in the upper side and two in the lower side of the jaw. At this time he has his full set of milk temporary teeth, consisting of twelve molars or grinders and twelve incisors or front teeth, six above and six below, making twenty-four in all. As the colt advances in age he sheds all these teeth. He then commences to get permanent teeth. When the age of one year is reached, four permanent molars appear, two in each jaw, one on each side, behind the three temporary teeth. At two years of age he gets four more back molars, one on each side of each jaw. When the age of two years and nine months is reached the two middle teeth of the temporary incisors, or front teeth of each jaw fall out, and are replaced by two permanent incisors in each jaw; thus at the age of three years these four permanent incisors are up and in wear. At this age, the first eight molars, two on each side of each jaw, are shed and replaced by eight permanent molars. At four years of age he sheds four more front or incisor teeth next to those shed at three years, and these are replaced by four more permanent incisors or front teeth. At this age, too, he sheds the four remaining temporary molars, or grinders, which are replaced by four more permanent molars. He also gets four more permanent molars at the back of the mouth. Thus at the age of four years the colt has a full set of permanent molars, consisting of six on each side of each jaw, making twenty-four in all. At five years of age he sheds the four remaining temporary incisors or front teeth, which are replaced by four permanent incisors, known as the corner teeth. It is important to become familiar with the time at which the colt sheds his different teeth, for sometimes the caps or shells of the teeth do not fall off when they should. These should be watched, for they greatly interfere with feeding and should be removed with forceps. At five years of age the canine or bridle teeth make their appearance; thus at the age of five years the colt has all his teeth or what is known as a full mouth.

The following table shows the various changes taking place in the mouth of the horse from the time of birth up to the age of five years:

Hence the horse has—

The table given below indicates the various changes which occur in the mouths of ruminants, and more particularly in the mouth of the ox:

RUMINANTS

A table giving the number and variety of teeth as they occur in the domestic animals and in man may be serviceable as one of handy reference, and is herewith appended:

The dental formula of the ox is the same as that of all ruminants.

RESPIRATORY SYSTEM OF THE HORSE.

Organs of Respiration.—By the action of these organs certain chemical and physical changes take place in the blood, the chief of these consisting of absorption of oxygen from, and giving off carbonic acid to the atmospheric air, the former change 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. Thus insects breathe by air-tubes, opening on the surface of the body; in the oyster breathing is performed by fringes; in fishes by gills; in the mammalia by means of elastic air-receptacles, called lungs, which are enclosed in special cavities, and communicate with the atmosphere by means of an air-tube.

In the horse, who breathes only through his nose, the organs of respiration are the nostrils, nasal-chambers, larynx, trachea, and in the thoracic cavity, the bronchi, bronchial tubes, and the lungs.

Nostrils.—The nostrils are two openings, one on each side of the nose. They are held open by the aid of cartilage and muscles. About one and one-half inches up the nostril on the under side is a small opening about the size of a grain of shot. Through this opening the duct or tube which carries the tears down from the eyes empties into the nose. The nostril is lined with a thin, delicate skin which changes into mucous membrane as it passes up into the chambers of the head.

Nasal Chambers.—These give passage to the air from the nostril into the larynx. There are two of these chambers, divided in the center by a thin partition or cartilage called the septum nasi. These communicate with the sinuses of the head. The horse cannot breathe through the mouth on account of the formation of the throat, and this compels him to always breathe through the nostrils. This is a point which should be remembered.

Larynx.—This is a cavity made of cartilage. It gives passage to the air and also the organ of voice. It is situated in the floor of the gullet. This cavity has an opening on its upper side, guarded by a valve, which is always opened except when the animal is swallowing food or water. When the food is being swallowed it passes over the valve which closes the opening while the food passes over it. This is important, for if the valve does not close properly, thus allowing either food or water to drop into the windpipe, the animal will have a fit of coughing. This is sometimes referred to as “the food going down the wrong way.” On the outside of this cavity of cartilage are found several small muscles which help to hold it in its place. It is lined inside by a continuation of the same membrane as that of the chambers of the head. The vocal cords which come into play when the animal is whinnying are found along the inside of this cavity. These cords are not nearly so well marked as in the human being, and if they or the cartilage of the larynx become affected it generally gives rise to the disease called wind-broken or roaring.

Trachea (Windpipe).—This is a tube which conveys the air down from the larynx to the bronchial tubes in the lungs. It is made up of forty or fifty rings of cartilage which are united to each other by strong elastic ligaments. They give to the windpipe its flexibility, that is, the power to bend in any direction almost like a piece of elastic. From the larynx the windpipe enters the chest where it terminates into two small tubes, one going to the right lung and one to the left. These are called the bronchial tubes.

Bronchial Tubes and Air Cells.—These are made up of the same material as that of the windpipe, but are only about half the size. After passing into the substance of the lungs they break up into small tubes which pass all through the lungs and terminates into what is known as the air-cells. These small tubes and air cells are lined inside by a very thin mucous membrane, a continuation of the membrane lining the other organs already mentioned. Just inside this thin mucous membrane is found the capillary network of the lungs, and while the blood is slowly passing through this network of vessels it gives off to the air in the air cells carbonic acid gas and takes in the oxygen from the pure air while it is in the lungs.

Lungs.—Lungs are the most important organs of respiration. They are spongy, yellowish organs, two in number, one situated on the right side, and the other on the left. The right lung is the largest because of the left one having a hollow in its side for the heart. The lungs are separated by a partition known as the mediastinum, by the heart which is in the folds of this partition, and also the large blood vessels and oesophagus. They are made up of light elastic tissue and are full of air cells and tubes. While the animal is alive they are very large and fill up nearly the whole chest cavity, but after death they collapse and are not nearly so large. Between the lungs and the ribs is found a serous membrane called the pleura or the lining membrane of the chest. It is made up of two folds, one being attached around the outer surface of the lungs, while the other is attached to the ends of the ribs at the side and at the back to the large curtain which separates the lungs from the bowels. The little glands situated in this membrane secrete an oily fluid which serves to lubricate these parts while the lungs are working in the chest so as not to cause friction. When this membrane becomes inflamed from a chill or injury it sets up the disease called pleurisy.

Respiration.—The number of respirations per minute varies with the different classes of animals; as a rule, the larger the animal the slower the respiration.

The rate of breathing is increased from the process of digestion immediately after eating, or may increase from exercise.

RESPIRATORY SYSTEM OF THE OX.

The nostrils are narrow and capable of little dilation compared to those of the horse. The nasal chambers differ chiefly in there being an additional turbinated bone. The nasal chambers communicate with the mouth, therefore cattle can breathe through the mouth to a certain extent. The larynx is simpler in construction, the true vocal cords being only slightly developed. The trachea or windpipe presents no important variation. We may note the presence of a third bronchus, which passes to the right lung to supply a lobe which is wanting in the horse.

The Thoracic Cavity is relatively smaller in the ruminants, and the pleurae present a very important deviation from the arrangement found in the solipede—viz., the back or posterior mediastinum is imperforate and strong, completely separating one pleural sac from the other. This arrangement exists in all the domesticated mammals but the solipede. The left lung is divided into two lobes, the right into four, the front one recurving over and almost covering the front of the heart. The interlobular or cellular tissue is exceedingly thick, the separation between the lobules being distinctly visible. This arrangement explains perfectly the special nature of pneumonic lesions in the large ruminants.

URINARY SYSTEM OF THE HORSE.

The organs of this system secrete the urine from the blood, and excrete or expel it from the body. These organs are chiefly the kidneys, ureters, bladder and urethra. The urine, which is a watery fluid, is secreted by the kidneys, and carried off by their ducts, the ureters, to a special reservoir, the bladder, where it accumulates and from which it is finally expelled at intervals through the urethra.

The kidneys are two compound tubular glands, one on the right side and one on the left side, and are situated just below the small of the back (sublumbar region), the right one being the fartherest ahead. In shape they are long and narrow and resemble the liver in color. In cutting one of the kidneys open, it is found to be full of glands and tubes, which secrete the urine from the blood while it is passing through the kidneys. These tubes pass to the center of the kidneys, where they empty the urine into what is called the pelvis. The glands are largely supplied with blood vessels and nerves. The use of the kidneys are to secrete the urine from the blood, which contains a large amount of what is known as ureaic acid, and if not taken out of the blood by these glands, acts as a poison to the system.

The Ureters are tubes which carry the urine down from the pelvis of the kidney to the bladder. They are two in number, one situated on the right side of the pelvic cavity and the other on the left side, close to the walls—they enter on each side at the upper surface of the bladder. They are only about one-sixteenth of an inch in diameter.

The Bladder is situated in the pelvic cavity. When it is full it sometimes stretches out into the abdominal cavity. It consists of a body and neck. The body is the large part, and is placed in front; the neck being at the back part of the bladder. This is where the urine passes out of the bladder. The bladder is made up of three coats, somewhat similar to that of the bowels. The serous coat is a continuation of the serous coat found in the abdominal cavity lining the bowels. The inside is lined with mucous membrane which is thrown into folds when the bladder is empty. Another coat is found between the two membranes above mentioned, called the muscular coat, the action of which is to contract the bladder when the animal wants to urinate. The bladder is held in by ligaments. The rectum lies above the bladder, which in the horse rests on the floor of the pelvic cavity. Its position in the mare differs from that of the horse. Instead of the rectum or back bowel being immediately above it, as in the horse, the womb is just above the bladder or between it and the rectum. The bladder acts as a reservoir in which to store the urine until it is full; it then presses on the walls and nerves, giving a peculiar sensation to these parts, causing the walls to contract, forcing the urine into a tube which carries it from the body. This is called the urethra. The neck of the bladder is simply an opening at the back part, and is guarded by a valve which prevents the urine from dripping out except when the animal is passing its urine or water.

The Urethra is the tube which carries the urine from the bladder out of the body. It is situated much differently in the mare than in the horse. In the mare it is very short, passing from the neck of the bladder along below the womb and vagina, which is the passage from the outside into the neck of the womb. It opens up into the underside of this passage about four inches in from the outside. This opening is guarded by a small, thin valve, and can be felt by passing the finger along the under side of the passage which leads into the womb. In the horse this tube is a great deal longer than in the mare. It commences at the bladder, passes along below the rectum or back bowel to just below the anus. Here this tube bends downward and forward and passes into the penis, continuing down to the end where it terminates. Its purpose is to carry the urine from the bladder out of the body and to perform certain actions in connection with the genital organs. Its lining is a continuation of the membrane of the bladder.

URINARY ORGANS OF THE OX.