THE LIVER. 



127 



but both larger and smaller branches, besides the main 

 trunk, into which they divide, give off a number of small 

 vessels at right angles. The latter, often after a very short 

 course, at once enter the hepatic islets contiguous to the 

 largest vascular canals, while the larger portal branches, 

 ramifying continually, and becoming finer and finer, have, 

 according to their diameter, to take a longer or a shorter 

 course through the hepatic parenchyma in the canals lined by 

 the capsule of Glisson, before they enter the hepatic islets or 

 lobules. Each of these receives, from one or other set of 

 vessels, at least 3, usually 4 — 5, smaller vessels of ^ — £"', 

 which Kiernan calls vena interlobular es. Such a vein, how- 

 ever, is never distributed to only one hepatic islet, but always 

 to two, or even three. Their ultimate branches, the rami 

 lobulares of Kiernan, 10 — 20 in number, enter the neighbouring 

 hepatic islets, usually at a right angle, and divide imme- 

 diately into the capillary network, without becoming, in man, 

 directly united with one another. In fact, the branches of 

 the portal vein nowhere anastomose, but are connected merely 

 by the finest vascular network of 

 the organ. 



The capillary network of the 

 islets (fig. 222) completely fills 

 the interspaces of the hepatic cell 

 network, so that the secreting 

 parenchyma consists actually of 

 only two elements, the hepatic 

 cells and the capillaries. Exactly 

 as the hepatic cell-network is con- 

 tinuous through the entire liver, 

 though, being interrupted by the 

 biliary ducts which pass off and 

 the vessels which enter, at regular 

 intervals, it is divided into separate, 

 very minute area — so the capillary 

 network of the blood-vessels passes from one hepatic islet to 

 another, but is nevertheless discontinuous in certain spots. 



Fig. 222. 



Fig. 222. Hepatic-cell network and its capillaries, x 350, from the Pig. Spaces 

 are purposely left here and there between the cells and capillaries, which do not 

 exist in nature. 



