BILE. 245 



intervals of digestion, to be expelled therefrom during the diges- 

 tive process. 



When the bile leaves the liver it is a clear fluid with a specific 

 gravity of 1010. During its stay in the gall-bladder it becomes 

 viscid, and loses some of its water and inorganic salts, certainly 

 some of the chlorids, which are absorbed by the gall-bladder, and 

 its specific gravity is increased to 1030 or 1040. The viscidity in 

 human bile is due to mucin, but that of ox's bile is due to an in- 

 gredient which was formerly thought to be mucin, but is now 

 regarded as a nucleoproteid. That it is not mncin is shown by 

 several facts : the nitrogen is from 14 to 16 per cent, higher than 

 in mucin, and when boiled with a mineral acid it does not yield 

 a reducing sugar. This substance is formed by the epithelial cells 

 lining the gall-bladder. 



FIG. 139. Portion of gall-bladder and bile-ducts: 1, cavity of gall-bladder; 2, 

 cavity of calyx; 3, groove separating the calyx from the bladder; 4, promontory; 

 5. superior valve of calyx ; 6, cystic canal ; 7, common bile-duct ; 8, hepatic duct 



(Testut). 



The bile is alkaline in reaction, sodium carbonate and alkaline 

 sodium phosphate being present to the extent of about 0.2 per 

 1000. Its color varies: in herbivorous animals it is green; in 

 carnivorous animals golden yellow or golden red ; while in man it 

 is of a golden yellow, though often green. 



Constituents of the Bile. The chemical composition of the bile 

 varies in the same individual at different times, and this differ- 

 ence depends, to a considerable extent, upon the length of time 



