266 EXCRETION. 



proportion of this principle in the bile is always very large, 

 though subject to considerable variation. It has very little 

 in common with the salts of fatty origin, either in its general 

 properties or composition, inasmuch as it is entirely insolu- 

 ble in ether, and its acid contains nitrogen. Another pecu- 

 liarity in its composition, and one which serves to distinguish 

 it from the glycocholate of soda, is that it contains two 

 atoms of sulphur. One of its important properties in the 

 bile is that it aids in the solution of the fats contained in 

 this fluid, and to a certain extent, probably, in the solution 

 of cholesterine. 



Glycocholate of Soda (NaO,0 M H 4r N"O n ). We have ne- 

 cessarily described the process for the extraction of the 

 glycocholate of soda, in connection with the taurocholate. 

 The glycocholate is crystallizable and is more easily obtained 

 in a condition of purity. The chief chemical points of dif- 

 ference between these salts are, that the glycocholate is pre- 

 cipitated by the acetate of lead as well as the subacetate, the 

 acetate having no effect upon the taurocholate of soda, and 

 that the glycocholic acid does not contain sulphur. By 

 treating glycocholic acid with potash at a high temperature, 

 it is decomposed into cholic acid and glycine, or glycocoll 

 (C 4 H 5 ]^0 4 ). It is this which has given it the name of glyco- 

 cholic acid. In their physiological relations, the two biliary 

 salts are, as far as we know, identical. 



Origin of the Biliary Salts. There can be no doubt 

 that these principles are elements of secretion, and are pro- 

 duced de novo in the substance of the liver. In no instance 

 have they ever been discovered in the blood in health ; and, 

 although they present certain points of resemblance with 

 some of the constituents of the urine, they have never been 

 found in the excreta. In experiments made by Miiller, 1 



1 MUELLER, Manual de physiologic, Paris, 1851, tome L, p. 122. 



