tt 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 jaw 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 



