hypodermically in
one-quarter grain doses every hour or two hours until the heart beats
are invigorated, the number and fullness of the respirations increased,
and consciousness returns. Stimulating injections per rectum may also be
useful in arousing the circulation; for this purpose whisky or ammonia
water may be used.

DISEASES OF THE HEART, BLOOD VESSELS, AND LYMPHATICS.

By M. R. TRUMBOWER, V. S.

[Revised by Leonard Pearson, B. S., V. M. D.]

ANATOMY AND PHYSIOLOGY OF THE HEART AND BLOOD VESSELS.

(Pls. XX and XXI.)

The heart is a hollow, muscular organ, situated a little to the left of
the center of the chest. Its impulse is felt on the left side on account
of its location and from the rotary movement of the organ in action. It
is cone-shaped, with the base upward; the apex points downward,
backward, and to the left side. It extends from about the third to the
sixth ribs, inclusive. The average weight is about 7 to 8 pounds. In
horses used for speed the heart is relatively larger, according to the
weight of the animal, than in horses used for slow work. It is suspended
from the spine by the large blood vessels and held in position below by
the attachment of the pericardium to the sternum. It is inclosed in a
sac, the pericardium, which is composed of a dense fibrous membrane
lined by a delicate serous membrane, which is reflected over the heart;
the inner layer is firmly adherent to the heart, the outer to the
fibrous sac, and there is an intervening space, known as the pericardial
space, in which a small amount of serum--a thin translucent liquid--is
present constantly.

The heart is divided by a shallow fissure into a right and left side;
each of these is again subdivided by a transverse partition into two
compartments which communicate. Thus there are four cardiac
cavities--the superior, or upper, ones called the auricles; the
inferior, or lower, ones the ventricles. These divisions are marked on
the outside by grooves, which contain the cardiac blood vessels, and are
generally filled with fat.

The right side of the heart may be called the venous side, the left the
arterial side, named from the kind of blood which passes through them.
The auricles are thin-walled cavities placed at the base, and are
connected with the great veins--the venae cavae and pulmonary
veins--through which they receive blood from all parts of the body. The
auricles communicate with the ventricles each by a large ape