Special Report on Diseases of the Horse | Page 7

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