Chapter 2

Gas collects under the skin in some instances. This comes from a local inoculation with an organism which produces a fermentation beneath the skin and causes the liberation of gas which inflates the skin, or the gas may be air that enters through a wound penetrating some air-containing organ, as the lungs. The condition here described is known as emphysema. Emphysema may follow the fracture of a rib when the end of a bone is forced inward and caused to penetrate the lung, or it may occur when, as a result of an ulcerating process, an organ containing air is perforated. This accident is more common in cattle than it is in horses. Emphysema is recognized by the fact that the swelling that it causes is not hot or sensitive on pressure. It emits a peculiar crackling sound when it is stroked or pressed upon.

Wounds of the skin may be of importance in the diagnosis of internal disease. Wounds over the bony prominence, as the point of the hip, the point of the shoulder, and the greatest convexity of the ribs, occur when a horse is unable to stand for a long time and, through continually lying upon his side, has shut off the circulation to the portion of the skin that covers parts of the body that carry the greatest weight, and in this way has caused them to mortify. Little, round, soft, doughlike swellings occur on the skin and may be scattered freely over the surface of the body when the horse is afflicted with urticaria. Similar eruptions, but distributed less generally, about the size of a silver dollar, may occur as a symptom of dourine, or colt distemper. Hard lumps, from which radiate welt-like swellings of the lymphatics, occur in glanders, and blisterlike eruptions occur around the mouth and pasterns in horsepox.

THE ORGANS OF CIRCULATION.

The first item in this portion of the examination consists in taking the pulse. The pulse may be counted and its character may be determined at any point where a large artery occupies a situation close to the skin and above a hard tissue, such as a bone, cartilage, or tendon. The most convenient place for taking the pulse of the horse is at the jaw. The external maxillary artery runs from between the jaws, around the lower border of the jawbone, and up on the outside of the jawbone to the face. It is located immediately in front of the heavy muscles of the cheek. Its throb can be felt most distinctly just before it turns around the lower border of the jawbone. The balls of the first and second or of the second and third fingers should be pressed lightly on the skin over this artery when its pulsations are to be studied.

The normal pulse of the healthy horse varies in frequency as follows:

Stallion 28 to 32 beats per minute.

Gelding 33 to 38 beats per minute.

Mare 34 to 40 beats per minute.

Foal 2 to 3 years old 40 to 50 beats per minute.

Foal 6 to 12 months old 45 to 60 beats per minute.

Foal 2 to 4 weeks old 70 to 90 beats per minute.

The pulse is accelerated by the digestion of rich food, by hot weather, exercise, excitement, and alarm. It is slightly more rapid in the evening than it is in the morning. Well-bred horses have a slightly more rapid pulse than sluggish, cold-blooded horses. The pulse should be regular; that is, the separate beats should follow each other after intervals of equal length, and the beats should be of equal fullness, or volume.

In disease, the pulse may become slower or more rapid than in health. Slowing of the pulse may be caused by old age, great exhaustion, or excessive cold. It may be due to depression of the central nervous system, as in dumminess, or be the result of the administration of drugs, such as digitalis or strophantus. A rapid pulse is almost always found in fever, and the more severe the infection and the weaker the heart the more rapid is the pulse. Under these conditions, the beats may rise to 80, 90, or even 120 per minute. When the pulse is above 100 per minute the outlook for recovery is not promising, and especially if this symptom accompanies high temperature or occurs late in an infectious disease. In nearly all of the diseases of the heart and in anemia the pulse becomes rapid.

The pulse is irregular in diseases of the heart, and especially where the valves are affected. The irregularity may consist in varying intervals between the beats or the dropping of one or more beats at regular or irregular intervals. The latter condition sometimes occurs in chronic diseases of the brain. The pulse is said to be weak, or soft, when the beats are indistinct, because little blood is forced through the artery by each contraction of the heart. This condition occurs when there is a constriction of the vessels leading from the heart and it occurs in certain infectious and febrile diseases, and is an indication of heart weakness.

In examining the heart itself it is necessary to recall that it lies in the anterior portion of the chest slightly to the left of the median line and that it extends from the third to the sixth rib. It extends almost to the breastbone, and a little more than half of the distance between the breastbone and the backbone. In contracting, it rotates slightly on its axis, so that the point of the heart, which lies below, is pressed against the left chest wall at a place immediately above the point of the elbow. The heart has in it four chambers--two in the left and two in the right side. The upper chamber of the left side (left auricle) receives the blood as it comes from the lungs, passes it to the lower chamber of the left side (left ventricle), and from here it is sent with great force (for this chamber has very strong, thick walls) through the aorta and its branches (the arteries) to all parts of the body. The blood returns through the veins to the upper chamber of the right side (right auricle), passes then to the lower chamber of the right side (right ventricle), and from this chamber is forced into the lungs to be oxidized. The openings between the chambers of each side and into the aorta are guarded by valves.

If the horse is not too fat, one may feel the impact of the apex of the heart against the chest wall with each contraction of the heart by placing the hand on the left side back of the fifth rib and above the point of the elbow. The thinner and the better bred the horse is the more distinctly this impact is felt. If the animal is excited, or if he has just been exercised, the impact is stronger than when the horse is at rest. If the horse is weak, the impact is reduced in force.

The examination of the heart with the ear is an important matter in this connection. Certain sounds are produced by each contraction of the normal heart. It is customary to divide these into two, and to call them the first and second sounds. These two sounds are heard during each pulsation, and any deviation of the normal indicates some alteration in the structure or the functions of the heart. In making this examination, one may apply the left ear over the heavy muscles of the shoulder back of the shoulder joint, and just above the point of the elbow, or, if the sounds are not heard distinctly, the left fore leg may be drawn forward by an assistant and the right ear placed against the lower portion of the chest wall that is exposed in this manner.

The first sound of the heart occurs while the heart muscle is contracting and while the blood is being forced from the heart and the valves are rendered taut to prevent the return of the blood from the lower to the upper chambers. The second sound follows quickly after the first and occurs during rebound of blood in the arteries, causing pressure in the aorta and tensions of the valves guarding its opening into the left ventricle. The first sound is of a high pitch and is longer and more distinct than the second. Under the influence of disease these sounds may be altered in various ways. It is not profitable, in a work such as this, to describe the details of these alterations. Those who are interested will find this subject fully discussed in the veterinary textbooks.

TEMPERATURE.

The temperature of the horse is determined roughly by placing the fingers in the mouth or between the thighs or by allowing the horse to exhale against the cheek or back of the hand. In accurate examination, however, these means of determining temperature are not relied upon, but recourse is had to the use of the thermometer. The thermometer used for taking the temperature of a horse is a self-registering clinical thermometer, similar to that used by physicians, but larger, being from 5 to 6 inches long. The temperature of the animal is measured in the rectum.

The normal temperature of the horse varies somewhat under different conditions. It is higher in the young animal than in the old, and is higher in hot weather than in cold. The weather and exercise decidedly influence the temperature physiologically. The normal temperature varies from 99.5° to 101° F. If the temperature rises to 102.5° the horse is said to have a low fever; if the temperature reaches 104° the fever is moderate; if it reaches 106° it is high, and above this point it is regarded as very high. In some diseases, such as tetanus or sunstroke, the temperature goes as high as 108° or 110°. In the ordinary infectious diseases it does not often exceed 106°. A temperature of 107.5° and above is very dangerous and must be reduced promptly if the horse is to be saved.

THE ORGANS OF RESPIRATION.

In examining this system of organs and their functions it is customary to begin by noting the frequency of the respiratory movements. This point can be determined by observing the motions of the nostrils or of the flanks; on a cold day one can see the condensation of the moisture of the warm air as it comes from the lungs. The normal rate of respiration for a healthy horse at rest is from 8 to 16 per minute. The rate is faster in young animals than in old, and is increased by work, hot weather, overfilling of the stomach, pregnancy, lying upon the side, etc. Acceleration of the respiratory rate where no physiological cause operates is due to a variety of conditions. Among these is fever; restricted area of active lung tissue, from filling of portions of the lungs with inflammatory exudate, as in pneumonia; compression of the lungs or loss of elasticity; pain in the muscles controlling the respiratory movements; excess of carbon dioxid in the blood; and constriction of the air passages leading to the lungs.

Difficult or labored respiration is known as dyspnea. It occurs when it is difficult, for any reason, for the animal to obtain the amount of oxygen that it requires. This may be due to filling of the lungs, as in pneumonia; to painful movements of the chest, as in rheumatism or pleurisy; to tumors of the nose and paralysis of the throat, swellings of the throat, foreign bodies, or weakness of the respiratory passages, fluid in the chest cavity, adhesions between the lungs and chest walls, loss of elasticity of the lungs, etc. Where the difficulty is great the accessory muscles of respiration are brought into play. In great dyspnea the horse stands with his front feet apart, with his neck straight out, and his head extended upon his neck. The nostrils are widely dilated, the face has an anxious expression, the eyeballs protrude, the up-and-down motion of the larynx is aggravated, the amplitude of the movement of the chest walls increased, and the flanks heave.

The expired air is of about the temperature of the body. It contains considerable moisture, and it should come with equal force from each nostril and should not have an unpleasant odor. If the stream of air from one nostril is stronger than from the other, there is an indication of an obstruction in a nasal chamber. If the air possesses a bad odor, it is usually an indication of putrefaction of a tissue or secretion in some part of the respiratory tract. A bad odor is found where there is necrosis of the bone in the nasal passages or in chronic catarrh. An ulcerating tumor of the nose or throat may cause the breath to have an offensive odor. The most offensive breath occurs where there is necrosis, or gangrene, of the lungs.

In some diseases there is a discharge from the nose. In order to determine the significance of the discharge it should be examined closely. One should ascertain whether it comes from one or both nostrils. If but from one nostril, it probably originates in the head. The color should be noted. A thin, watery discharge may be composed of serum, and it occurs in the earlier stages of coryza, or nasal catarrh. An opalescent, slightly tinted discharge is composed of mucus and indicates a little more severe irritation. If the discharge is sticky and puslike, a deeper difficulty or more advanced irritation is indicated. If the discharge contains flakes and clumps of more or less dried, agglutinated particles, it is probable that it originates within a cavity of the head, as the sinuses or guttural pouches. The discharge of glanders is of a peculiar sticky nature and adheres tenaciously to the wings of the nostrils. The discharge of pneumonia is of a somewhat red or reddish brown color and, on this account has been described as a prune-juice discharge. The discharge may contain blood. If the blood appears as clots or as streaks in the discharge, it probably originates at some point in the upper part of the respiratory tract. If the blood is in the form of a fine froth, it comes from the lungs.

In examining the interior of the nasal passage one should remember that the normal color of the mucous membrane is a rosy pink and that its surface is smooth. If ulcers, nodules, swellings, or tumors are found, these indicate disease. The ulcer that is characteristic of glanders is described fully in connection with the discussion of that disease.

Between the lower jaws there are several clusters of lymphatic glands. These glands are so small and so soft that it is difficult to find them by feeling through the skin, but when a suppurative disease exists in the upper part of the respiratory tract these glands become swollen and easy to feel. They may become soft and break down and discharge as abscesses; this is seen constantly in strangles. On the other hand, they may become indurated and hard from the proliferation of connective tissue and attach themselves to the jawbone, to the tongue, or to the skin. This is seen in chronic glanders. If the glands are swollen and tender to pressure, it indicates that the disease causing the enlargement is acute; if they are hard and insensitive, the disease causing the enlargement is chronic.

The manner in which the horse coughs is of importance in diagnosis. The cough is a forced expiration, following immediately upon a forcible separation of the vocal cords. The purpose of the cough is to remove some irritant substance from the respiratory passages, and it occurs when irritant gases, such as smoke, ammonia, sulphur vapor, or dust, have been inhaled. It occurs from inhalation of cold air if the respiratory passages are sensitive from disease. In laryngitis, bronchitis, and pneumonia, cough is very easily excited and occurs merely from accumulation of mucus and inflammatory product upon the irritated respiratory mucous membrane. If one wishes to determine the character of the cough, it can easily be excited by pressing upon the larynx with the thumb and finger. The larynx should be pressed from side to side and the pressure removed the moment the horse commences to cough. A painful cough occurs in pleurisy, also in laryngitis, bronchitis, and bronchial pneumonia. Pain is shown by the effort the animal exerts to repress the cough. The cough is not painful, as a rule, in the chronic diseases of the respiratory tract. The force of the cough is considerable when it is not especially painful and when the lungs are not seriously involved. When the lungs are so diseased that they can not be filled with a large volume of air, and in heaves, the cough is weak, as it is also in weak, debilitated animals. If mucus or pus is coughed out, or if the cough is accompanied by a gurgling sound, it is said to be moist; it is dry when these characteristics are not present--that is, when the air in passing out passes over surface not loaded with secretion.

In the examination of the chest we resort to percussion and auscultation. When a cask or other structure containing air is tapped upon, or percussed, a hollow sound is given forth. If the cask contains fluid, the sound is of a dull and of quite a different character. Similarly, the amount of air contained in the lungs can be estimated by tapping upon, or percussing, the walls of the chest. Percussion is practiced with the fingers alone or with the aid of a special percussion hammer and an object to strike upon known as a pleximeter. If the fingers are used, the middle finger of the left hand should be pressed firmly against the side of the horse and should be struck with the ends of the fingers of the right hand bent at a right angle so as to form a hammer. The percussion hammer sold by instrument makers is made of rubber or has a rubber tip, so that when the pleximeter, which is placed against the side, is struck the impact will not be accompanied by a noise. After experience in this method of examination one can determine with a considerable degree of accuracy whether the lung contains a normal amount of air or not. If, as in pneumonia, air has been displaced by inflammatory product occupying the air space, or if fluid collects in the lower part of the chest, the percussion sound becomes dull. If, as in emphysema, or in pneumothorax, there is an excess of air in the chest cavity, the percussion sound becomes abnormally loud and clear.

Auscultation consists in the examination of the lungs with the ear applied closely to the chest wall. As the air goes in and out of the lungs a certain soft sound is made which can be heard distinctly, especially upon inspiration. This sound is intensified by anything that accelerates the rate of respiration, such as exercise. This soft, rustling sound is known as vesicular murmur, and wherever it is heard it signifies that the lung contains air and is functionally active. The vesicular murmur is weakened when there is an inflammatory infiltration of the lung tissue or when the lungs are compressed by fluid in the chest cavity. The vesicular murmur disappears when air is excluded by the accumulation, of inflammatory product, as in pneumonia, and when the lungs are compressed by fluid in the chest cavity. The vesicular murmur becomes rough and harsh in the early stages of inflammation of the lungs, and this is often the first sign of the beginning of pneumonia.

By applying the ear over the lower part of the windpipe in front of the breastbone a somewhat harsh, blowing sound may be heard. This is known as the bronchial murmur and is heard in normal conditions near the lower part of the trachea and to a limited extent in the anterior portions of the lungs after sharp exercise. When the bronchial murmur is heard over other portions of the lungs, it may signify that the lungs are more or less solidified by disease and the blowing bronchial murmur is transmitted through this solid lung to the ear from a distant part of the chest. The bronchial murmur in an abnormal place signifies that there exists pneumonia or that the lungs are compressed by fluid in the chest cavity.

Additional sounds are heard in the lungs in some diseased conditions. For example, when fluid collects in the air passages and the air is forced through it or is caused to pass through tubes containing secretions or pus. Such sounds are of a gurgling or bubbling nature and are known as mucous râles. Mucous râles are spoken of as being large or small as they are distinct or indistinct, depending upon the quantity of fluid that is present and the size of the tube in which this sound is produced. Mucous râles occur in pneumonia after the solidified parts begin to break down at the end of the disease. They occur in bronchitis and in tuberculosis, where there is an excess of secretion.

Sometimes a shrill sound is heard, like the note of a whistle, fife, or flute. This is due to a dry constriction of the bronchial tubes and it is heard in chronic bronchitis and in tuberculosis.

A friction sound is heard in pleurisy. This is due to the rubbing together of roughened surfaces, and the sound produced is similar to a dry rubbing sound that is caused by rubbing the hands together or by rubbing upon each other two dry, rough pieces of leather.

THE EXAMINATION OF THE DIGESTIVE TRACT.

The first point in connection with the examination of the organs of digestion is the appetite and the manner of taking food and drink. A healthy animal has a good appetite. Loss of appetite does not point to a special diseased condition, but comes from a variety of causes. Some of these causes, indeed, may be looked upon as being physiological. Excitement, strange surroundings, fatigue, and hot weather may all cause loss of appetite. Where there is cerebral depression, fever, profound weakness, disorder of the stomach, or mechanical difficulty in chewing or swallowing, the appetite is diminished or destroyed. Sometimes there is an appetite or desire to eat abnormal things, such as dirty bedding, roots of grass, soil, etc. This desire usually comes from a chronic disturbance of nutrition.

Thirst is diminished in a good many mild diseases unaccompanied by distinct fever. It is seen where there is great exhaustion or depression or profound brain disturbance. Thirst is increased after profuse sweating, in diabetes, diarrhea, in fever, at the crises of infectious diseases, and when the mouth is dry and hot.

Some diseases of the mouth or throat make it difficult for the horse to chew or swallow his feed. Where difficulty in this respect is experienced, the following named conditions should be borne in mind and carefully looked for: Diseases of the teeth, consisting in decay, fracture, abscess formation, or overgrowth; inflammatory conditions, or wounds or tumors of the tongue, cheeks, or lips; paralysis of the muscles of chewing or swallowing; foreign bodies in upper part of the mouth between the molar teeth; inflammation of throat. Difficulty in swallowing is sometimes shown by the symptom known as "quidding." Quidding consists in dropping from the mouth well-chewed and insalivated boluses of feed. A mouthful of hay, for example, after being ground and masticated, is carried to the back part of the mouth. The horse then finds that from tenderness of the throat, or from some other cause, swallowing is difficult or painful, and the bolus is then dropped from the mouth. Another quantity of hay is similarly prepared, only to be dropped in turn. Sometimes quidding is due to a painful tooth, the bolus being dropped from the mouth when the tooth is struck and during the pang that follows. Quidding may be practiced so persistently that a considerable pile of boluses of feed accumulate in the manger or on the floor of the stall. In pharyngitis one of the symptoms is a return through the nose of fluid that the horse attempts to swallow.

In some brain diseases, and particularly in chronic internal hydrocephalus, the horse has a most peculiar manner of swallowing and of taking feed. A similar condition is seen in hyperemia of the brain. In eating the horse will sink his muzzle into the grain in the feed box and eat for a while without raising the head. Long pauses are made while the feed is in the mouth. Sometimes the horse will eat very rapidly for a little while and then slowly; the jaws may be brought together so forcibly that the teeth gnash. In eating hay the horse will stop at times with hay protruding from the mouth and stand stupidly, as though he has forgotten what he was about.