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.
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,