THE VETERINARY SCIENCE 
auricle communicates with the left ventricle, same as • on 
the right side. The right side of the heart is sometimes 
called the venous; this side contains only impure blood. The 
left side is sometimes called the arterial side. It deals with 
pure blood only. This side of the heart is very much stronger 
and thicker than the right side. 
2. Arteries. — Arteries are strong tubes the purpose of 
which is to carry the blood from the heart. For this reason 
it is apparent that all arteries carry pure or arterial blood 
with but one exception. The pulmonary artery carries the 
blood from the right ventricle to the lungs and consequently 
carries impure or venous blood. Each time the left ventricle • 
contracts it causes a wave, as it were, to pass all through 
the arteries. This contraction takes place when in a healthy 
condition about 38 to 40 times every minute and gives rise 
to what is known as the pulse. This wave, or beating, may 
be detected at any point where the artery is situated so 
closely to the surface as to affect the outside of the body 
sufficient to be felt by placing the finger on the point, con- 
sequently the pulse may be counted at any of these points. 
Place your forefinger on the lower edge of your own lower 
jaw directly under the corner of your mouth. At this point 
an artery passes out over the jaw bone and therefore runs 
very close to the surface, making it quite possible to feel the 
wave caused by the contraction of your own heart, quite 
distinctly. Near this point on the javv^ of the horse the pulse 
is most conveniently felt and counted. 
The walls of the arteries are composed of elastic tissue 
and after death are always lying open. Blood is never found 
in them after death because they continue to contract suffi- 
ciently long enough to force all the blood through them. 
3. Veins. — Veins are tubes — in construction not so strong 
as the arteries — the purpose of which is to carry the blood 
from all parts of the body to the heart. The heart wave 
does not affect the veins and consequently the pulse cannot 
be detected by placing the finger on an exposed portion of 
one of them. It is also apparent that all veins carry impure 
or venous blood with but one exception, viz. : the pulmonary 
vein, the purpose of which is to conduct the purified blood 
from the lungs to the heart. 
4. Capillaries. — The capillaries form a connecting link 
between the arteries and veins. Toward the end, the arteries 
