CH. XXXIII.] FUNCTIONS OF THE LIVER 507 



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 plasma 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 extirpa- 

 tion of the liver they do not accumulate in the blood. 



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

 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. 



Schiifer states that the liver-cells contain not only the intra- 

 cellular bile-canaliculi, but also intracellular blood-canaliculi passing 

 off from the capillaries between the cells. These are too minute to 

 admit blood-corpuscles. 



The Gall-bladder (G. B., fig. 401) 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. Its wall is constructed of three coats. (1) 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 meta- 

 bolism of the body, especially in connection with the metabolism of 

 carbohydrates (glycogenic function); and in connection with the 

 metabolism of nitrogenous material (formation of urea and uric acid). 

 This second function we shall discuss with the urine. The third 

 function is the formation of bile, which must very largely be regarded 

 as a subsidiary one, bile containing the waste products of the liver, 



