Chapter 1

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U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY.

A. D. MELVIN, CHIEF OF BUREAU.

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SPECIAL REPORT

ON

DISEASES OF THE HORSE.

BY

Drs. PEARSON, MICHENER, LAW, HARBAUGH, TRUMBOWER, LIAUTARD, HOLCOMBE, HUIDEKOPER, MOHLER, EICHHORN, HALL, AND ADAMS.

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REVISED EDITION, 1916.

WASHINGTON: GOVERNMENT PRINTING OFFICE. 1916.

DEPARTMENT OF AGRICULTURE,

_Washington, March 30, 1916._

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Transcriber's note: The italic markup for single italized letters are deleted for easier reading. Minor typos have been corrected and footnotes moved to the end of the sections.

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This edition of the Special Report on Diseases of the Horse has been prepared in compliance with House Concurrent Resolution No. 13, passed February 3, 1916, as follows:

_Resolved by the House of Representatives (the Senate concurring)_, That there be printed and bound in cloth one hundred thousand copies of the Special Report on the Diseases of the Horse, the same to be first revised and brought to date, under the supervision of the Secretary of Agriculture; seventy thousand copies for the use of the House of Representatives and thirty thousand for use of the Senate.

Since the original edition issued by the Department in 1890 several editions have been printed by order of Congress. The work was reprinted in 1896, and revised and reprinted in 1903, 1908, and 1911. In accordance with the foregoing resolution it again has been revised so as to embody the latest practical development of knowledge of the subject.

D. F. HOUSTON,

_Secretary._

CONTENTS.

Page.

The examination of a sick horse. By Leonard Pearson 7

Fundamental principles of disease. By Rush Shippen Huidekoper 27

Methods of administering medicines. By Ch. B. Michener 44

Diseases of the digestive organs. By Ch. B. Michener 49

Diseases of the respiratory organs. By W. H. Harbaugh 95

Diseases of the urinary organs. By James Law 134

Diseases of the generative organs. By James Law 164

Diseases of the nervous system. By M. R. Trumbower 210

Diseases of the heart, blood vessels, and lymphatics. By M. R. Trumbower 247

Diseases of the eye. By James Law 274

Lameness. By A. Liautard 298

Diseases of the fetlock, ankle, and foot. By A. A. Holcombe 395

Diseases of the skin. By James Law 458

Wounds and their treatment. By Ch. B. Michener 484

Infectious diseases. By Rush Shippen Huidekoper 507

Shoeing. By John W. Adams 583

Index 607

ILLUSTRATIONS.

PLATES.

Page. PLATE I. Inflammation 32

II. Inflammation 32

III. Digestive apparatus 48

IV. Age of horses as indicated by teeth 58

V. Intestinal worms 92

VI. Bots 92

VII. Position of the left lung 112

VIII. Longitudinal section through kidney 136

IX. Microscopic anatomy of kidney 136

X. Microscopic anatomy of kidney 136

XI. Calculi and instrument for removal 152

XII. Normal presentation 192

XIII. Some factors in difficult labor 192

XIV. Instruments used in difficult labor 192

XV. Abnormal presentations 200

XVI. Abnormal presentations 200

XVII. Abnormal presentations 200

XVIII. Abnormal presentations 200

XIX. The nervous system 216

XX. Interior of chest, showing position of heart and diaphragm 248

XXI. Circulatory apparatus 248

XXII. Diagrammatic vertical section through horse's eye 277

XXIII. Skeleton of horse 304

XXIV. Superficial layer of muscles 304

XXV. Splint 312

XXVI. Ringbone 312

XXVII. Various types of spavin 312

XXVIII. Bone spavin 312

XXIX. Bone spavin 312

XXX. Dislocation of shoulder and elbow, Bourgelat's apparatus 360

XXXI. The sling in use 360

XXXII. Anatomy of foot 400

XXXIII. Anatomy of foot 400

XXXIV. Anatomy and diseases of foot 400

XXXV. Sound and contracted feet 400

XXXVI. Quarter crack and remedies 432

XXXVII. Foundered feet 432

XXXVIII. The skin and its diseases 458

XXXIX. Mites that infest the horse 480

XL. Glanders 544

XLI. Glanders 544

XLII. Glanders 544

TEXT FIGURES.

Page. FIG. 1. Ground surface of a right fore hoof of the "regular" form 590

2. Pair of fore feet of regular form in regular standing position 591

3. Pair of fore feet of base-wide form in toe-wide standing position 591

4. Pair of fore feet of base-narrow form in toe-narrow standing position 592

5. Side view of an acute-angled fore foot, of a regular fore foot, and of a stumpy fore foot 592

6. Side view of foot with the foot-axis broken backward as a result of too long a toe 595

7. Left fore hoof of a regular form, shod with a plain fullered shoe 599

8. Side view of hoof and fullered shoe 599

9. An acute-angled left fore hoof shod with a bar shoe 601

10. A fairly formed right fore ice shoe for a roadster 601

11. Left fore hoof of regular form shod with a rubber pad and "three-quarter" shoe 602

12. A narrow right fore hoof of the base-wide standing position shod with a plain "dropped crease" shoe 602

13. Hoof surface of a right hind shoe to prevent interfering 603

14. Ground surface of shoe shown in fig. 13 603

15. Side view of a fore hoof shod so as to quicken the "breaking over" in a "forger" 604

16. Side view of a short-toed hind hoof of a forger 604

17. A toe-weight shoe to increase the length of stride of fore feet 605

18. Most common form of punched heel-weight shoe to induce high action in fore feet 605

SPECIAL REPORT ON DISEASES OF THE HORSE.

THE EXAMINATION OF A SICK HORSE.

By Leonard Pearson, B. S., V. M. D.

In the examination of a sick horse it is important to have a method or system. If a definite plan of examination is followed one may feel reasonably sure, when the examination is finished, that no important point has been overlooked and that the examiner is in a position to arrive at an opinion that is as accurate as is possible for him. Of course, an experienced eye can see, and a trained hand can feel, slight alterations or variations from the normal that are not perceptible to the unskilled observer. A thorough knowledge of the conditions that exist in health is of the highest importance, because it is only by a knowledge of what is right that one can surely detect a wrong condition. A knowledge of anatomy, or of the structure of the body, and of physiology, or the functions and activities of the body, lie at the bottom of accuracy of diagnosis. It is important to remember that animals of different races or families deport themselves differently under the influence of the same disease or pathological process. The sensitive and highly organized thoroughbred resists cerebral depression more than does the lymphatic draft horse. Hence a degree of fever that does not produce marked dullness in a thoroughbred may cause the most abject dejection in a coarsely bred, heavy draft horse. This and similar facts are of vast importance in the diagnosis of disease and in the recognition of its significance.

The order of examination, as given hereafter, is one that has proved to be comparatively easy of application and sufficiently thorough for the purpose of the readers of this work, and is recommended by several writers.

HISTORY.

It is important to know, first of all, something of the origin and development of the disease; therefore the cause should be looked for. The cause of a disease is important, not only in connection with diagnosis, but also in connection with treatment. The character of feed that the horse has had, the use to which he has been put, and the kind of care he has received should all be closely inquired into. It may be found by this investigation that the horse has been fed on damaged feed, such as brewers' grains or moldy silage, and this may be sufficient to explain the profound depression and weakness that are characteristic of forage poisoning. If it is learned that the horse has been kept in the stable without exercise for several days and upon full rations, and that he became suddenly lame in his back and hind legs, and finally fell to the ground from what appeared to be partial paralysis, this knowledge, taken in connection with a few evident symptoms, will be enough to establish a diagnosis of azoturia (excess of nitrogen in the urine). If it is learned that the horse has been recently shipped in the cars or has been through a dealer's stable, we have knowledge of significance in connection with the causation of a possible febrile disease, which is, under these conditions, likely to prove to be influenza, or edematous pneumonia.

It is also important to know whether the particular horse under examination is the only one in the stable, or on the premises, that is similarly afflicted. If it is found that several horses are afflicted much in the same way, we have evidence of a common cause of disease which may prove to be of an infectious nature.

Another item of importance in connection with the history of the case relates to the treatment that the horse may have had before he is examined. It sometimes happens that medicine given in excessive quantities produces symptoms resembling those of disease, so it is important that the examiner be fully informed as to the medication that has been employed.

ATTITUDE AND GENERAL CONDITION.

Before beginning the special examination, attention should be paid to the attitude and general condition of the animal. Sometimes horses assume positions that are characteristic of a certain disease. For example, in tetanus (lockjaw) the muscles of the face, neck, and shoulders are stiff and rigid, as well as the muscles of the jaw. This condition produces a peculiar attitude, that once seen is subsequently recognized as rather characteristic of the disease. A horse with tetanus stands with his muscles tense and his legs in a somewhat bracing position, as though he were gathered to repel a shock. The neck is stiff and hard, the head is slightly extended upon it, and the face is drawn, and the nostrils are dilated. The tail is usually held up a little, and when pressed down against the thighs it springs back to its previous position. In inflammation of the throat, as in pharyngolaryngitis, the head is extended upon the neck and the angle between the jaw and the lower border of the neck is opened as far as possible to relieve the pressure that otherwise would fall upon the throat. In dumminess, or immobility, the hanging position of the head and the stupid expression are rather characteristic. In pleurisy, peritonitis, and some other painful diseases of the internal organs, the rigid position of the body denotes an effort of the animal to avoid pressure upon and to protect the inflamed sensitive region.

The horse may be down in the stall and unable to rise. This condition may result from paraplegia (paralysis), from azoturia, from forage poisoning, from tetanus, or from painful conditions of the bones or feet, such as osteoporosis or founder. Lying down at unusual times or in unusual positions may indicate disease. The first symptom of colic may be a desire on the part of the horse to lie down at an unusual or inappropriate time or place. Sometimes disinclination to lie down is an indication of disease. When there is difficulty in breathing, the horse knows that he can manage himself better upon his feet than upon his breast or his side. It happens, therefore, that in nearly all serious diseases of the respiratory tract he stands persistently, day and night, until recovery has commenced and breathing is easier, or until the animal falls from sheer exhaustion. If there is stiffness and soreness of the muscles, as in rheumatism, inflammation of the muscles from overwork, or of the bones in osteoporosis, or of the feet in founder, or if the muscles are stiff and beyond control of the animal, as in tetanus, a standing position is maintained, because the horse seems to realize that when he lies down he will be unable to rise.

Abnormal attitudes are assumed in painful diseases of the digestive organs (colic). A horse with colic may sit upon his haunches, like a dog, or may stand upon his hind feet and rest upon his knees in front, or he may endeavor to balance himself upon his back, with all four feet in the air. These positions are assumed because they give relief from pain by lessening pressure or tension upon the sensitive structures.

Under the general condition of the animal it is necessary to observe the condition or state of nutrition, the conformation, so far as it may indicate the constitution, and the temperament. By observing the condition of nutrition one may be able to determine to a certain extent the effect that the disease has already had upon the animal and to estimate the amount of strength that remains and that will be available for the repair of the diseased tissues. A good condition of nutrition is shown by the rotundity of the body, the pliability and softness of the skin, and the tone of the hair. If the subcutaneous fat has disappeared and the muscles are wasted, allowing the bony prominences to stand out; if the skin is tight and inelastic and the coat dry and harsh, we have evidence of a low state of nutrition. This may have resulted from a severe and long-continued disease or from lack of proper feed and care. When an animal is emaciated--that is, becomes thin--there is first a loss of fat and later the muscles shrink. By observing the amount of shrinkage in the muscles one has some indication as to the duration of the unfavorable conditions under which the animal has lived.

By constitution we understand the innate ability of the animal to withstand disease or unfavorable conditions of life. The constitution depends largely upon the conformation. The type of construction that usually accompanies the best constitution is deep, broad chest, allowing plenty of room for the lungs and heart, indicating that these vital organs are well developed; capacious abdomen, allowing sufficient space for well-developed organs of digestion; the loins should be short--that is, the space should be short between the last rib and the point of the hip; the head and neck should be well molded, without superfluous or useless tissue; this gives a clear-cut throat. The ears, eyes, and face should have an expression of alertness and good breeding. The muscular development should be good; the shoulders, forearms, croup, and thighs must have the appearance of strength. The withers are sharp, which means that they are not loaded with useless, superfluous tissue; the legs are straight and their axes are parallel; the knees and hocks are low, which means that the forearms and thighs are long and the cannons relatively short. The cannons are broad from in front to behind and relatively thin from side to side. This means that the bony and tendinous structures of the legs are well developed and well placed. The hoofs are compact, tense, firm structures, and their soles are concave and frogs large. Such a horse is likely to have a good constitution and to be able to resist hard work, fatigue, and disease to a maximum degree. On the other hand, a poor constitution is indicated by a shallow, narrow chest, small bones, long loins, coarse neck and head, with thick throat, small, bony, and muscular development, short thighs and forearms, small joints, long, round cannons, and hoofs of open texture with flat soles.

The temperament is indicated by the manner in which the horse responds to external stimuli. When the horse is spoken to, or when he sees or feels anything that stimulates or gives alarm, if he responds actively, quickly, and intelligently, he is said to be of lively, or nervous, temperament. On the other hand, if he responds in a slow, sluggish manner, he is said to have a sluggish, or lymphatic, temperament. The temperament is indicated by the gait, by the expression of the face, and by the carriage of the head and ears. The nature of the temperament should be taken into consideration in an endeavor to ascertain the severity of a given case of illness, because the general expression of an animal in disease as well as in health depends to a large extent on the temperament.

THE SKIN AND THE VISIBLE MUCOUS MEMBRANES.

The condition of the skin is a fair index to the condition of the animal. The effect of disease and emaciation upon the pliability of the skin have been referred to above. There is no part of the body that loses its elasticity and tone as a result of disease sooner than the skin. The practical herdsman or flockmaster can gain a great deal of information as to the condition, of an animal merely by grasping the coat and looking at and feeling the skin. Similarly, the condition of the animal is shown to a certain extent by the appearance of the mucous membranes. For example, when the horse is anemic as a result of disease or of inappropriate feed the mucous membranes become pale. This change in the mucous membranes can be seen most readily in the lining of the eyelids and in the lining of the nostril. For convenience of examination the eyelids can readily be everted. Paleness means weak circulation or poor blood. Increased redness occurs physiologically in painful conditions, excitement, and following severe exertion. Under such conditions the increase of circulation is transitory. In fevers there is an increased redness in the mucous membrane, and this continues so long as the fever lasts. In some diseases red spots or streaks form in the mucous membrane. This usually indicates an infectious disease of considerable severity, and occurs in blood poisoning, purpura hemorrhagica, hemorrhagic septicemia, and in urticaria. When the liver is deranged and does not operate, or when the red-blood corpuscles are broken down, as in serious cases of influenza, there is a yellowish discoloration of the mucous membrane. The mucous membranes become bluish or blue when the blood is imperfectly oxidized and contains an excess of carbon dioxid. This condition exists in any serious disease of the respiratory tract, as pneumonia, and in heart failure.

The temperature of the skin varies with the temperature of the body. If there is fever the temperature of the skin is likely to be increased. Sometimes, however, as a result of poor circulation and irregular distribution of the blood, the body may be warmer than normal, while the extremities (the legs and ears) may be cold. Where the general surface of the body becomes cold it is evident that the small blood vessels in the skin have contracted and are keeping the blood away, as during a chill, or that the heart is weak and is unable to pump the blood to the surface, and that the animal is on the verge of collapse.

The skin is moist, to a certain degree, at all times in a healthy horse. This moisture is not in the form of a perceptible sweat, but it is enough to keep the skin pliable and to cause the hair to have a soft, healthy feel. In some chronic diseased conditions and in fever, the skin becomes dry. In this case the hair has a harsh feel that is quite different from the condition observed in health, and from the fact of its being so dry the individual hairs do not adhere to one another, they stand apart, and the animal has what is known as "a staring coat." When, during a fever, sweating occurs, it is usually an indication that the crisis is passed. Sometimes sweating is an indication of pain. A horse with tetanus or azoturia sweats profusely. Horses sweat freely when there is a serious impediment to respiration; they sweat under excitement, and, of course, from the well-known physiological causes of heat and work. Local sweating, or sweating of a restricted area of the body, denotes some kind of nerve interference.

Swellings of the skin usually come from wounds or other external causes and have no special connection with the diagnosis of internal diseases. There are, however, a number of conditions in which the swelling of the skin is a symptom of a derangement of some other part of the body. For example, there is the well-known "stocking," or swelling of the legs about the fetlock joints, in influenza. There is the soft swelling of the hind legs that occurs so often in draft horses when standing still and that comes from previous inflammation (lymphangitis) or from insufficient heart power. Dropsy, or edema of the skin, may occur beneath the chest or abdomen from heart insufficiency or from chronic collection of fluid in the chest or abdomen (hydrothorax, ascites, or anemia). In anasarca or purpura hemorrhagica large soft swellings appear on any part of the skin, but usually on the legs, side of the body, and about the head.