418 



THE DIGESTIVE SYSTEM 



central vein. The central vein frequently begins in the form of a Y, 

 its two or more branches finally uniting to form a single vessel which 

 pursues its course through the axis of the lobule. The central vein 

 makes its exit at the periphery of the lobule and enters the interlobular 

 connective tissue where it unites with its fellows to form larger sub- 

 lobular veins. The sublobular are easily distinguished from the inter- 

 lobular veins by their thicker walls and by the fact that the former 



fi'* 



FIG. 393. A SUBLOBULAR VEIN OF THE PIG'S LIVER. 



a, capsule of Glisson between adjacent lobules. Hematein and eosin. Photo. 

 X 60. 



pursue an independent course through the tissue of Glisson's capsule, 

 being nowhere in relation with either artery or duct. 



The sublobular veins are, as a rule, vessels of considerable size, and 

 by frequent union with their fellows become constantly larger. In their 

 general direction they tend toward the dorsal surface of the liver and 

 finally make their exit as four or five large hepatic veins which enter 

 the inferior vena cava. 



The blood supply of the liver, 30 per cent, of which can be ac- 

 counted for in the hepatic artery, GO per cent, in the portal vein (Mac- 



