THE DIGESTIVE SECRETIONS 



939 



hepatic cells themselves. Eventually the capillaries of the hepatic artery unite 

 into channels which empty directly into the terminals of the portal vein at the 

 periphery of each lobule. So united they form the central or intralobular veins, 

 and these in turn the hepatic veins. This anastomosis between the hepatic arterial 

 and portal systems accounts for the fact that the secretory power of this organ 

 cannot be destroyed by the ligation of the aforesaid vein. Under these circum- 

 stances, the arterial blood finds its way in greater quantity into the portal channels, 

 thereby compensating in part for the loss of the portal blood. ^ 



The nerve supply of the liver is derived from the celiac ganglion of the solar 

 plexus. The individual postganglionic fibers ascend along the hepatic artery 

 around which they form an intricate plexus. At the hilum of this organ they 

 ramify extensively, forming here the so-called hepatic plexus. Distally to this 

 point they follow the branches of the hepatic artery 

 in order to gain the interior of the different lobes of 

 this organ. 



Of special interest to us at this time is 

 the fact that the hepatic cells lie in direct 

 contact with these intralobular capillaries, 

 and furthermore, since the lining of these 

 vessels is in many places deficient, the blood 

 is brought into direct communication with 

 the contents of these cells. These deficiencies 

 account for the fact that perfectly intact 

 red corpuscles may be found inside their 

 cytoplasm. Here and there along these 

 vessels we also note the so-called stellate cells 

 of Kupffer which are large phagocytic bodies 

 capable of ingesting red cells and other solid 

 particles contained in the blood. Hence, it 

 cannot surprise us to find that coloring fluids 

 injected through the portal vein may be 

 traced directly into the interior of these cells 

 where they produce delicate canalicuh or 

 sinusoids. In this organ, therefore, the 

 lymph does not play the part of a middle- 

 man between the blood and the cells. 



On the other side of these radial rows of secretory cells are the 

 biliary spaces and capillaries which convey their characteristic se- 

 cretion, the bile, into the larger collecting channels. While many his- 

 tologists state that these delicate tubules arise in secreting vacu- 

 oles within the cytoplasm of these cells, others claim that they begin 

 as blind spaces between two adjoining rows of cells. Farther outward 

 they acquire a lining of columnar epithelium as well as a basement- 

 membrane and fibrous and smooth muscle tissue. In many animals, 

 the larger biliary ducts empty into a special reservoir which is known 

 as the gall-bladder. The liver is also plentifully supplied with lym- 

 phatics which accompany the capillaries of the portal vein as well 

 as those of the hepatic artery. These two systems communicate 



1 Burton-Opitz, Quart. Jour, of Exp. Physiol., iv, 1911, 93. 



Fig. 500. — Diagram to 

 Illustrate the Relation of 

 THE Portal Terminals (P) 

 TO THE Biliary Capillaries 

 (B). The Arrows Indicate 

 THE Direction op the Flow. 



