Special Report on Diseases of the Horse | Page 6

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