280 



DIGESTION. 



The bile varies in color and consistence in different animals. It usually has a greenish, 

 yellowish, or brownish hue. In the human subject, it has a dark, golden-brown color 

 and is somewhat viscid in consistence, chiefly from admixture with the mucus of the gall- 

 bladder. The specific gravity of human bile has been found to be about 1018. Its reac- 

 tion is faintly alkaline. 



Physiological chemists have long since recognized in the bile peculiar principles, 

 which are found in no other part of the organism ; but the exact nature of these con- 

 stituents was first described by Strecker, in 1848, who obtained from the bile of the ox 

 two principles, cholic and choleic acid, which he found to exist in this fluid in combina- 

 tion with soda. The cholic acid of Strecker, which may be decomposed into a new acid 

 and a principle called glycine, and the choleic acid, from which may be formed a new 

 acid and taurine, are called by Lehmann, respectively, glycocholic and taurocholic acid. 

 In the bile of the ox, these are found combined with soda, and the peculiar proximate 

 principles of this fluid are now recognized as the glycocholate of soda, a crystalline sub- 

 stance, and the taurocholate of soda, which is of a resinous consistence and is stated to 

 be uncrystallizable. In the human bile, Dalton has found a resinous substance, which, 

 from its behavior with various reagents, is undoubtedly analogous to the taurocholate 

 of soda of ox-bile, but which he could not obtain in a crystalline form. 



FIG. 11. Crystals oj glycocholate of soda. (Eobin.) 



In addition to the biliary salts, the bile contains the ordinary inorganic salts, found 

 in nearly all the animal fluids, a small quantity of fat, the oleates, margarates, and stea- 

 rates of soda and potassa, mucus from the gall-bladder, and cholesterine ; the last being 

 an excrementitious product. The action of the bile in digestion, whatever its nature may 



