THE VASCULAR SYSTEM. 



The vascular system is composed of the central forcing 

 muscular organ, the heart; a system of vessels, the 

 arteries, carrying the blood from the ventricles to the 

 lungs and all parts of the body; a system of vessels, the 

 veins, returning the blood to the auricles; and numerous 

 microscopic vessels, the capillaries, connecting the 

 termination of the arteries with the origin of the veins. 



THE HEART. 



The location of the heart in the cat may be seen by 

 removing the ventral thoracic wall, but for the study 

 of the parts, the heart of an ox or a sheep will be found 

 more satisfactory. The heart of the cat lies between 

 the lungs (Fig. 80) in the thoracic cavity a little to the 

 left of the median line. The caudal end is the apex, and 

 the cephalic end is the base. The entire organ is in- 

 vested by a tough membrane, the pericardium, which 

 when cut permits the pericardial fluid to run out. All 

 the blood-vessels originate from the dorsocephalic aspect 

 of the heart. 



It is composed of a right and left half, each of which 

 consists of an auricle and a ventricle. The separation 

 between the two halves is apparent on the ventral 

 surface. The auricles receive the blood from the veins 

 and pass it to the ventricles, which disperse it through 

 the arteries. There is no aperture between the auricles 

 or the ventricles. The aperture between the right 



auricle and the right ventricle is guarded by the tricuspid 



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