262 DIGESTIVE SYSTEM. 



alkalinity which has led to the supposition that it has an 

 important share in the process of digestion. 



It may be said, briefly, to be composed of water, containing 

 in solution three different elements : salts, cholesterine, and 

 coloring matter. 1 



1. The salts of the bile are essentially what was formerly 

 designated under the name of biline : this biline is now 

 shown (Demargnis) to be a combination of soda with two 

 fatty acids, cholic acid and choleic acid: these constitute the 

 cholate and choleate of soda; these acids are also designated 

 under the names of Taurocholic and Glycocholic (Tauro- 

 cholate and Glycocholate of Soda) both being formed by the 

 same acid, united in the one case, to glycochol, and, in the 

 other, to taurine. In fishes these acids are combined, not 

 with soda, but with potash. 



It is generally admitted that the cholalic acid is originated 

 in fatty substances ; indeed, it is found strongly to resemble 

 the oleic acid, for instance; it is not, therefore, a nitrogenous 

 substance. Glycochol we know to be a nitrogenous sub- 

 stance, having a sweetish taste, and being derived from 

 collagen ous substances, whence the name of sugar of gela- 

 tine. Taurine is, also, a nitrogenous or azotic principle, but 

 it also contains sulphur, and its decomposition in the intes- 

 tine assists in producing sulphuretted hydrogen. 



2. Cholesterine is a fatty substance which is not saponifi- 

 able ; it is insoluble in water, but soluble in bile, on account 

 of the choleate of soda existing in the latter; if the quantity 

 of this salt is insufficient, the cholesterine is precipitated, 

 forming those calculi so frequently found in the biliary reser- 

 voir. Researches by Flint seem to show that cholesterine is 

 a waste produced by the life of the nervous elements (see p. 

 27). 



3. The coloring matter is essentially represented by biU- 

 fulvine, a substance strongly resembling the blood pigment 

 (haematoin) from which it is derived; it is decomposed 

 and precipitated very readily, yielding then various coloring 

 matters, designated as bilirubine, biliverdine, etc. : green is 

 the color most frequently found in decomposed bile. 



1 Table showing the chemical composition of the bile : 



Water 85 per cent. 



Coloring matter, bilirubine 2 



