THE BILE. 



203 



the union of these two elements is intimate and complete throughout 

 the substance of the hepatic lobule. 



There is an equally close connection between the glandular substance 

 of the liver and the biliary ducts. The main hepatic duct, which with 

 its ramifications accompanies the divisions of the portal vein, breaks up 

 into branches which finally reach the interlobular spaces. The biliary 

 ducts in the human liver which have a larger diameter than about 200 

 mmm. are lined with cells of cylindrical epithelium ; while in those 

 which are below 100 mmm. in diameter, the form of the cells changes 

 gradually to that of pavement epithelium. The biliary ducts which 

 occupy the interlobular spaces are of the smaller variety, being not 

 more than 50 mmm. in diameter, and are lined accordingly with pave- 

 ment epithelium. They break up into communicating branches which 

 cover the surface of the lobule with a plexus of biliary canaliculi. 



Fig. 67. 



FINER BILIARY CANALS AND BILIARY DTTCTS, from the frog's liver. a. Small 

 biliary duct, with its lining of epithelium cells. 6, c. Terminal branches of the minute bili- 

 ary canals, surrounded by glandular cells, d. Transverse communicating branch between 

 two biliary canals, e, e. Sheath of glandular secreting cells, surrounding the biliary canals. 

 /. Section of capillary bloodvessel. (Eberth.) 



From this superficial plexus the finest biliary tubes penetrate into the 

 substance of the lobule and there inosculate with each other between 

 the glandular secreting cells. In the liver of the amphibia (frogs and 

 water-lizards), as shown by the investigations of Hering and Eberth, the 

 Itimate structure of the secreting apparatus is not essentially different 

 from that of other lobulated glands. The smaller biliary ducts, lined 

 with pavement epithelium, give off minute branches which communicate 

 with each other more or less abundantly and are themselves in contact 

 everywhere with the large glandular cells ; each terminal branch being 



