178 MANUAL OP PHYSIOLOGY. 



Composition of Bile. The bile of man and carnivorous 

 animals is of a deep orange-red color, turning to greenish-brown 

 by decomposition of its coloring matter. In herbivorous animals 

 it has some shade of green when quite fresh, but turns to a muddy 

 brown after a time. It is transparent, and more or less viscid, 

 according to the length of time it has remained in the gall 

 bladder. It has a strong, bitter taste, a peculiar aromatic odor, 

 and after remaining for some time in the gall bladder it has an 

 alkaline reaction. Its specific gravity is about 1005 when taken 

 from the bile ducts directly, but it may rise to 1030 after pro- 

 longed stay in the gall bladder, owing to the addition of mucus 

 and the absorption of some of its fluid. 



The following table gives approximately the proportions of the 

 chief constituents of the bile : 



Water, 85.0 per cent. 



Bile salts, 10.0 " 



Coforing matter and mucus, 3.0 " 



Fats, 1.0 " 



Cholesterin, 0.3 " 



Inorganic salts, 0.7 " 



100.0 



Bile contains no structural elements nor any trace of albumin- 

 ous bodies. 



I. The bile acids are two compound acids, glycocholic and 

 taurocholic, which exist in the bile in combination with sodium. 

 The amount of each varies in different animals and at different 

 times in the same animal. The bile of the dog and other car- 

 nivora contains only taurocholate of soda. In the ox the glyco- 

 cholate of soda is greatly in excess. In man both are present, 

 the proportion being variable, but the glycocholate greatly pre- 

 ponderates. 



To separate these acids, bile is evaporated to one-fourth its 

 volume, rubbed to a paste with animal charcoal to remove the 

 pigments, and carefully dried. The black cake is extracted with 

 absolute alcohol, which dissolves the bile salts. From the strong 

 alcoholic solution after partial evaporation the bile salts can be 

 precipitated by ether. They first appear as an emulsion, and 



