212 ELEMENTARY PHYSIOLOGY les& 



of the hepatic artery follow a course parallel to that of 

 the portal vein and finally, reaching the surface of a 

 lobule, pour the blood they carry into the lobular 

 capillaries. 



Thus the venous blood of the portal vein and the 

 arterial blood of the hepatic artery reach the surfaces of 

 the lobules by the ultimate branches of that vein and 

 artery, become mixed in the capillaries of each loljule, 

 and are carried off by its intralobular veinlet, which pours 

 its contents into one of the branches of the hepatic vein. 

 These branches, joining together, form lai'ger and larger 

 trunks, which at length reach the hinder margin of the 

 liver, and finally open into the vena cava inferior, 

 where it passes upwards in contact with that part of the 

 organ. 



Thus tiie blood with which the liver is supplied is a 

 mixture of arterial and venous blood : the former brought 

 by the hepatic artery directly frt)m the aorta, the latter 

 by the portal vein from the capillaries of the stomach, 

 intestines, pancreas, and spleen. 



In the lobules themselves all the meshes of the blood- 

 vessels are occupied by the liver cells, or hepatic cells. 

 These are many-sided minute bodies, each about 25/i(Yf5^gth 

 of an inch) in diameter, possessing a nucleus in its 

 interior, and frequently having larger and smaller gran- 

 ules of fatty matter distributed through its substance 

 (Fig. (54, B, a). Tt is in the liver cells that the active 

 powers of the liver reside. 



The smaller branches of the hepatic duct, lined by an 

 epithelium, wliich is continuous with that of the main 

 duct, and thence with that of the intestines, into which 

 the main duct opens, may be traced to the very surface of 

 the lobules, where they seem to end abruptly (Fig. 66). 

 But, upon closer examination, it is found that they 

 communicate with a network of minute passages passing 

 between the hepatic cells, and traversing the lobule in 

 the intervals left by the capillaries (Fig. 64, B, c). These 



