ANATOMY OF THE HEART AND BLOOD-VESSELS 



301 



This is the portion which goes through the stomach, spleen, pan- 

 creas, and intestines. After traversing the capillaries of those 

 organs it is collected into the portal vein which enters the liver, and 

 breaking up in it into finer and finer branches like an artery, ends 

 in the capillaries of that organ, forming the second set which this 

 blood passes through on its course. From these it is collected by 

 the hepatic veins, which pour it into the in- 

 ferior vena cava, which carries it to the 

 right auricle, so that it has still to pass 

 through the pulmonary capillaries to get 

 back to the left side of the heart. The 

 portal vein is the only one in the Human 

 Body which like an artery feeds a capillary 

 network, and the flow from the stomach 

 and intestines through the liver to the vena 

 cava is often spoken of as the portal circu- 

 lation. 



Diagram of the Circulation. Since the 

 two halves of the heart are actually com- 

 pletely separated from one another by an 

 impervious partition, although placed in 

 proximity in the Body, we may conven- 

 iently represent the course of the blood 

 as in the accompanying diagram (Fig. 108), showing that it forms a 



. . . ,, i i <*, i i c ji single closed circuit with 



in which the right and left halves of the two pumps in it, consisting 

 heart are represented at different points \ Sl^faret? 

 in the vascular system. Such an arrange- resented separate m the 



. ^ diagram, ra and rv, right 



ment makes it clear that the heart is really auricle and ventricle -la and 



i . . i i - v Iv, left auricle and ventri- 



two pumps working side by side, each en- cle . ^ aorta . sc sys temic 

 gaged in forcing the blood to the other. f ^^S^! 

 Starting; from the left auricle, la, and fol- pulmonary capillaries; pv, 



, . ., ^ ' T ,, pulmonary veins. 



lowing the flow, we trace it through the 



left ventricle and along the branches of the aorta into the sys- 

 temic capillaries, sc; from thence it passes back through the sys- 

 temic veins, vc. Reaching the right auricle, ra, it is sent into the 

 right ventricle, rv, and thence through the pulmonary artery, pa, 

 to the lung capillaries, pc, from which the pulmonary veins, pv, 

 carry it to the left auricle, which drives it into the left ventricle, Iv, 

 and this again into the aorta. 



