10 SECRETION OF BILE. 



(approximate composition of gastric peptone in 100 parts Carbon 49, 

 Hydrogen 7, Nitrogen 15, Oxygen 28, Sulphur i). It is soluble in water in 

 all proportions ; insoluble in alcohol or ether. Its solution diffuses readily : 

 it is unaffected by heat ; and, when acidulated with acetic acid, is not pre- 

 cipitated by ferrocyanide of potassium. It is precipitated by tannin bases, by 

 lead acetate, and by solution of Hg I 2 in iodide of potassium. 



Secretion of Bile. 



Human bile contains 10 per cent, of solids, of which 

 about 4 per cent, is bilin, i^ per cent, fat, 2 per cent, 

 mucus and colouring matter, i to 2 per cent, alkaline 

 soaps, i per cent, salts. It is believed that about two 

 pounds of bile are secreted daily. The density of bile 

 differs according to the mode of collection and the time 

 of secretion. Bilin and fat originate, along with other 

 bodies, from proteid in the living substance of the liver 

 cells. The colouring matter is derived from that of the 

 blood. The mucin is secreted by the mucous membrane 

 of the gall bladder. In the intestines the bilin is decom- 

 posed under the influence of septic ferment organisms: 

 glycin and taurin are absorbed, and either return to their 

 source, or may take part in the production of such bodies 

 as hippuric acid, and tauro-carbamic acid, which appear in 

 the urine ; cholalic acid is in great part lost in the faeces. 

 The fats and soaps are absorbed. The colouring matter is 

 transformed by reduction into a body having the char- 

 acters of hydrobilirubin. 



In intestinal digestion the bile is antiseptic, and there 

 is reason to believe that it also promotes the absorption 

 of fat. 



Nothing is as yet known as to the influence of the 

 nervous system on the secretion of bile. 



BILIN. 



Bilin (or Bile crystals], as obtained from ox bile, consists chiefly of sodic 

 glycocholate (C K H 42 Na NO 6 ), with a much smaller proportion of tauro- 

 cholate (C 26 H 44 Na NO 7 S). Bilin of dogs' bile consists exclusively of 

 taurocholate. These soap-like bodies crystallize from the alcoholic solution 



