5OO THE LIVER. [CH. XXXIII. 



between the hepatic cells and the bile-canaliculi is even more 

 intimate, for they have demonstrated the existence of vacuoles in 

 the cells communicating by minute intracellular channels with the 

 adjoining bile-canaliculi (fig. 410). It is important to notice that 

 the bile-canaliculi are always separated by at least a portion of a 

 cell from the nearest blood-capillaries, and that the formation of 

 bile is no mere transudation from the blood or lymph. The liver- 

 cells take certain materials from the lymph and elaborate the 

 constituents of the bile, the bile-salts and the bile pigments. 

 There can be no doubt that these substances are formed by the 

 hepatic cells, for they are not found in the blood nor in any other 

 organ or tissue ; and after extirpation of the liver they do not 

 accumulate in the blood. 



Intracellular canaliculi in the liver-cells are not unique. Recent 

 research by Golgi's method has shown that in the salivary and 

 gastric glands, and in the pancreas, there is a similar condition of 

 affairs. 



The Gall-bladder (G., B., fig. 403) is a pyriform bag, attached 

 to the under surface of the liver, and supported also by the 

 peritoneum, which passes below it. The larger end, or fundus, 

 projects beyond the front margin of the liver ; while the smaller 

 end contracts into the cystic duct. 



Structure. The walls of the gall-bladder are constructed of 

 three principal coats. ( i ) Externally (excepting that part which 

 is in contact with the liver) is the serous coat, which has the same 

 structure as the peritoneum with which it is continuous. Within 

 this is (2) the fibrous or areolar coat, with which is mingled a 

 considerable number of plain muscular fibres, both longitudinal 

 and circular. (3) Internally the gall-bladder is lined by mucous 

 membrane, and a layer of columnar epithelium. The surface of 

 the mucous membrane presents to the naked eye a minutely 

 honeycombed appearance from a number of tiny polygonal 

 depressions with intervening ridges, by which its surface is 

 mapped out. In the cystic duct the mucous membrane is raised 

 up in the form of crescentic folds, which together appear like 

 a spiral valve, and which assist the gall-bladder in retaining the 

 bile during the intervals of digestion. 



The gall-bladder and all the main biliary ducts are provided 

 with mucous glands, which open on the internal surface. 



Functions of the Liver. 



The functions of the liver are connected with the general 

 metabolism of the body ; these are especially in connection with 



