BILE. 501 



by the organic ingredients of the saliva. The saliva 

 stones of the horse and ass consist principally of cal- 

 cium carbonate with a little phosphate. 



5. Gastric Juice. 



The gastric juice, secreted by the small glands of 

 the mucous membrane of the stomach during diges- 

 tion, is a strongly acid, watery liquid, acid from the 

 presence of free lactic acid, and sometimes hydro- 

 chloric, butyric, and acetic acids. At the most it con- 

 tains 1.5 per cent, of solid ingredients. It contains a 

 great deal of common salt, small quantities of other 

 salts, and an organic matter (pepsin) of unknown 

 nature, which, in the presence of an acid, appears to 

 be the cause of the solvent action which the gastric 

 juice exercises upon articles of food otherwise insolu- 

 ble, as, for example, coagulated fibrin and albumen. 

 Water slightly acidified with hydrochloric acid, and 

 digested with a small piece of the mucous membrane 

 of the stomach, attains the property of dissolving 

 (digesting) coagulated fibrin and albumen, meat, etc., 

 transforming them into amorphous, white bodies 

 (peptone, parapeptone (p. 491), metapeptone), some of 

 which are soluble in water, and others in acids and 

 alkalies. Boiling temperature destroys this action. 



The mucous, alkaline, intestinal fluid has also the 

 property of causing the solution of protein compounds, 

 as well as converting starch into sugar, and sugar into 

 lactic and butyric acids. 



6. Bile. 



Bile is separated from the venous blood of the portal 

 vein in the liver. The liver consists of small cells, 

 which are arranged in net-like, adherent rows. In the 

 interstices between these cells are distributed the finest 

 beginnings of the biliary ducts, which conduct away 

 the secreted bile ; the finest branches of the portal 

 vein, from the blood of which the bile is secreted ; the 

 finest terminals of the hepatic artery, which convey 



