'54 



PHYSIOLOGY KOR IHCGINNERS 



portal vein, so that tlic distinction between one system and 

 the other is lost in the lobule, and the blood of one is mixed 

 with that of the other. The capillaries proceeding in this way 

 from the periphery to the centre of each lobule lie between 

 rows of the hepatic cells. In the centre of the lobule the 

 capillaries open into a vein which passes out of the lobule and 

 unites with similar veins from neighbouring lobules ; and in 

 this way larger veins are formed, which finally unite to form 



Fie. 70. Diagram to show the termination of a fine bile duct. 

 /', Small bile duct becoming still liner at l> ; /, hepatic cells ; c, capillaries cut across. 



the hepatic vein, which carries the blood from the liver to 

 the inferior vena cava. 



The branches of the bile duct, which consist of an internal 

 layer of columnar cells covered by a sheath of connective 

 tissue, can also be traced to the edge of the lobules, where 

 they begin as fine but distinct ducts, formed of a single layer 

 of cubical cells ; but these fine ducts are in communication 

 with minute, cleft-like passages between the hepatic cells of the 

 lobules. The fine passages between the cells of each lobule 

 unite to form the fine ducts just spoken of, which again unite, 

 forming larger ducts lying between the lobules, and these unite 

 with one another until the main bile duct is formed. The bile 

 duct which leads to the duodenum has, as we have said, close 

 to the liver, a side tube, which goes to the gall-bladder, 



