DIGESTION. 



271 



cava, just before its passage through the diaphragm. The swi-lobular 

 and hepatic veins, unlike the portal vein and its companions, have little 

 or no areolar tissue around them, and their coats being very thin, they 

 form little more than mere channels in the liver substance which closely 

 surrounds them. 



The manner in which the lobules are connected with the sub-lobular 

 veins by means of the small intra-lobular veins is well seen in the diagram 

 (Fig. 200 and in Fig. 201), which represent 

 the parts as seen in a longitudinal section. 

 The appearance has been likened to a twig 

 having leaves without footstalks the lobules 

 representing the leaves, and the sub-lobular 

 vein the small branch from which it springs. 

 On a transverse section, the appearance of the 

 intra-lobular veins is that of 1, Fig. 199, 

 while both a transverse and longitudinal sec- 

 tion are exhibited in Fig. 176. 



The hepatic artery, the function of which 

 is to distribute blood for nutrition to Glisson's 

 capsule, the walls of the ducts and blood- 

 vessels, and other parts of the liver, is distrib- 

 uted in a very similar manner to the portal 

 vein, its blood being returned by small branches either into the rami- 

 fications of the portal vein, or into the capillary plexus of the lobules 

 which connects the inter and infra lobular veins. 



FIG. 201. Diagram showing the 

 manner in which the lobules of the 

 liver rest on the sublobular veins. 

 (After Kiernan.) 



Fia. 202. Capillary network of the lobules of the rabbit's liver. The figure is taken from a very 

 successful injection of the hepatic veins, made by Harting: it shows nearly the whole of two lobules, 

 and parts of three others; p, portal branches running in the interlobular spaces; h, hepatic veins pen- 

 etrating and radiating from the centre of the lobules. X 45. (Kolliker.) 



The hepatic duct divides and subdivides in a manner very like that of 

 the portal vein and hepatic artery, the larger branches being lined by 

 cylindrical, and the smaller by small polygonal epithelium. 



