BILE CONSTITUENTS. 171 



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 

 then form glistening crystals which are soluble in water or alcohol, 

 but insoluble in ether. 



From the solution of the two salts the glyco-cholic acid may 

 be precipitated by neutral lead acetate, as lead glyco-cholate, 

 from which the lead may be removed by sulphuretted hydrogen, 

 and the acid precipitated from its alcoholic solution by the addi- 

 tion of water. The tauro-cholic acid may be obtained subse- 

 quently by treating with basic lead acetate. 



Glyco-cholic acid when boiled with weak acids, alkalies, or 

 baryta-water, takes up an atom of water, and splits into cholic 

 acid and glycin (amido-acetic acid). (See p. 66.) 



Tauro-cholic acid, under similar treatment, splits into cholic 

 acid and taurin (amido-ethyl-sulph.ouic acid). (See p. 65.) 



Cholic acid occurs free in the intestines, the bile salts being 

 split up in digestion and tauro-cholic and glyco-cholic acids sepa- 

 rated. 



The nitrogenous cholic acid is in a great measure eliminated 

 with the frcces, while the tauriu and glycin are reabsorbed into 

 the blood with many of the other constituents of 'the bile, and 

 are again probably utilized in the economy. 



No traces of these bile acids can be detected in normal blood, 

 and there is no accumulation of them in the body after the re- 

 moval of the liver; hence it has been concluded that they are 

 manufactured in the liver. 



II. Mucus. The greater part of the mucus which the bile con- 

 tains is produced in the gall bladder, and there added to the bile. 

 Some mucus comes from the mucous glands in the bile ducts, but 

 unless the bile has remained in the gall-bladder there is but an 

 insignificant amount of mucus present, as is seen when a fistula 

 is made from the hepatic duct. The mucus passes in an un 



