HUMAN LIVER 



177 



nective tissue are thrown outside the modified hepatic cells, and a bile- 

 duct results. The hepatic cells become, insensibly, the columnar 

 cells lining the duct. This is shown in the illustration rather 

 diagrammatically. Its demonstration requires much patient study 

 and search. The duct is best traced backwards to the point where 

 the bile -capillaries enter it. 



The study of the blood- and bile -capillaries of the liver is 

 much easier if tissues are used in which these vessels have been 

 injected with some colored substance. Injection of the bile -capil- 

 laries is difficult ; but injection of the blood -capillaries is quite 

 readily accomplished. 



The structure of the gall-bladder and its duct is substantially 

 the same as that of the larger bile -ducts. The mucous membrane 

 is thrown into numerous small folds, and is covered by columnar 

 epithelial cells. The mucous membrane is supplemented by 

 unstriated muscle -fibers, outside of which is a fibrous layer. 



