224 



THE HUMAN BODY. 



return there. This is the portion which goes through the 

 stomach, spleen, pancreas, 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 he- 

 patic veins, which pour it into the inferior vena cava, which 

 carries it to the right auricle, so that 

 it has still to pass through the pulmo- 

 nary 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 net- 

 work, and the flow from the stomach 

 and intestines through the liver to the 

 vena cava is often spoken of as the 

 portal circulation. 



Diagram of the Circulation. Since 

 the two halves of the heart are actu- 

 ally completely separated from one 

 another by an impervious partition, 

 although placed in proximity in the 

 Body, we may conveniently represent 

 the course of the blood as in the accom- 



FIG. 95.-Dia ff ram of the panying diagram (Fig. 95), in which 

 e the right and left halves of the heart 

 Et -are represented at different points in 

 which f Le a l; e P S resent e d ^ the vascular system. Such an arrange- 



T^ht^ri^Sd V^ridel meilt makeS lfc Clear th ^ fc the heaH 1S 



la and iv, left auricle and ven- reallv two pumps working ' .side bv side, 



tricle; ao, aorta; sc, systemic " , ," 



capillaries; vc, venae cavae; each engaged in forcing the blood to 

 pa, pulmonary artery; c, pul- ,, ? ru j- /> ii i 1. 



monary capillaries; pv, pui- the other, otarting ironi the lelt au- 

 ricle, la, and following the flow, we 



trace it through the left ventricle' and along the brunches of 

 the aorta into the systemic capillaries, sc', from thence it 

 passes back through the systemic veins, vc. Beaching the 

 right auricle, ra, it is sent into the right ventricle, rv, and 

 thence through the pulmonary artery, pa, to the lung .capilla- 

 ries, pc, from which the pulmonary veins, pv, carry i to the 

 left auricle, which drives it into the left ventricle, Iv, and this 

 again into the aorta. 



