Special Report on Diseases of the Horse | Page 7

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