164 



ANIMAL PHYSIOLOGY. 



salivary glands 



granules, and in the human subject distinct oil globules. 

 They have a radiating columnar arrangement in the lobules, 



an d pour their secre- 

 tion into a network 

 of minute intercellu- 

 lar channels, defi- 

 nitely walled, and 

 capable of being in- 

 jected; which, how- 

 ever, are not to be 

 considered as proper 

 secreting ducts, but 

 correspond with simi- 

 lar channels between 

 the cells contained 

 within the saccules of 

 the 

 and pancreas. 



In the livers of 

 many invertebrate 

 animals, the secreting 

 cells are obviously ar- 

 Fig. 87. A, HEPATIC STRUCTURE highly ranged in the form of 

 magnified; a a, section of capillaries ; an epithelial li n i ng O f 

 b, ft, intercellular channels (Hermg). B, , , , , -, -, % 

 Individual hepatic cells. a lobulated gland (fig. 



34), and there can be 



no doubt that the hepatic cells of vertebrata are morphologi- 

 cally comparable with these. An appearance of a limiting 

 membrane has even been demonstrated by one observer 

 (Beale), surrounding the columns within the lobules, and it 

 is legitimate to look on these columns as consisting of inter- 

 communicating tubules filled with secreting epithelium.; but 

 they are not so distinct as the blind extremities of any other 

 gland. 



Minute bile ducts, with independent walls, are seen between 

 the lobules; and these fall into ducts of larger size, copiously 

 beset with mucous glands. A right and left trunk emerge 

 from the corresponding lobes, and unite to form the hepatic 

 duct with which the gall bladder communicates by a duct of 

 ibs own, the cystic, to form with it the common bile duct. 



