BILE CONSTITUENTS. 179 



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

 but insoluble in ether. 



From the solution of the two salts the glycocholic acid may 

 be precipitated by neutral lead acetate, as lead glycocholate, 

 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 taurocholic acid may be obtained subsequently 

 by treating with basic lead acetate. 



Glycocholic acid when boiled with weak acids, alkalies, or 

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

 acid and glycin (arnido-acetic acid). (See p. 74.) 



Taurocholic acid, under similar treatment, splits into cholic 

 acid and taurin (amido-ethyl-sulphonic acid). (See p. 74.) 



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

 split up in digestion and taurocholic and glycocholic acids sepa- 

 rated. 



The non-nitrogenous cholic acid is in a great measure elimi- 

 nated with the faeces, while the taurin 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 blood, and 

 there is no accumulation of them in the body after the removal 

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

 factured 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 tne 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- 

 changed state through the intestine, and is evacuated with the 

 faeces. 



III. The bile pigment of man and carnivora is chiefly the red- 

 dish form called bilirubin. It is insoluble in water, but soluble 

 in chloroform. It can be obtained in rhombic crystals, and is 

 easily converted by oxidation into a green pigment, biliverdin, 

 which is the principal coloring matter in the bile of many ani- 



