298 THE ALIMENTARY CANAL, ETC. 



(2) The hepatic veins (Fig. 196 I and II) also course chiefly in 

 the middle parts of the lobes of the liver ; they branch, and ulti- 

 mately supply intralobular veins which interdigitate with the inter- 

 lobular veins (I and II). The capillaries arise very abruptly from 

 an intralobular vein, and form a network of vessels communicating 

 very freely with the corresponding capillaries of the interlobular 

 veins. 



(3) The hepatic arteries (Fig. 196 III) break up into small 

 branches which, as a rule, course along the portal canal until near 

 the surface of the liver, when they leave the portal veins and pass 

 to the surface to supply the coverings of the liver. In their course 

 along the portal canals they supply a few very small twigs to 

 the structures forming the canals. At the surface of the liver 

 the branches of the hepatic artery form capillaries, which empty 

 themselves into the general capillary anastomosis beneath (Fig. 

 196 III). 



8. The liver-cells (Figs. 197, 198) are large, and of compressed 

 spheroidal or polygonal shape. They possess no cell- wall, have 

 usually one but sometimes two large nuclei, each with a distinct 

 nucleolus. The cells often contain granules of glycogen or fat- 

 globules. The main fibrillae of the intercellular network are 



O 



arranged so as to extend between a bile-capillary and a blood- 

 capillary (Fig. 197)- 



e. The bile-ducts (Fig. 198) commence as fine tubes between the 

 liver-cells, where they are simply small spaces enclosed by the 

 hepatic cells; they are usually enclosed by three or four cells, 

 possibly sometimes by only two cells (Hering). Such bile-capillaries 

 are usually separated from a blood-capillary by the thickness of one 

 liver-cell only (Fig. 198). 



As a number of such bile-capillaries run together to form a larger 

 duct, the cells enclosing them change 1heir character, becoming 

 flattened and broader ; these cells may, however, be traced contin- 

 uously into the true hepatic cells (Hering and Eberth). The bile- 

 duct so formed then obtains a slight covering of fibrous tissue, 

 which rapidly increases in quantity, courses along a portal canal, 

 and receives other ducts on the way; the epithelium lining it 

 gradually becomes more elongated, and ultimately resembles that 

 found in the common bile-duct or the gall-bladder. 



In the larger ducts the epithelium is, according to v. Brunn, 



