THE BILE. 163 



Closely related to the common glycocholic acid is the so-called hyo- 

 glycocholic acid, which has been found in small amounts in the bile 

 of the pig. On decomposition it yields glycocoll and hyocholalic 

 acid, as shown in the equation : 



C 27 H 43 N0 5 + H 2 - C 2 H 5 N0 2 + C 25 H 40 O 4 

 Hyoglycocholic Glycocoll. Hyocholalic 



acid acid. 



The substance itself is almost insoluble in water, but soluble in 

 alcohol. It is crystallizable, but usually obtained as a resinous 

 mass. Its salts are precipitated from their solutions by calcium 

 chloride, barium chloride, and magnesium chloride. By salting 

 with sodium sulphate they separate out like soaps. Like the com- 

 mon glycocholates, they give Pettenkofer's reaction. 



In addition to these two forms still other glycocholates apparently 

 exist. In the bile of rodents a glycocholate is thus found, which 

 cannot be salted out with sodium sulphate, but which is also precipi- 

 tated by the salts of the alkaline earths. Of its nature, however, as 

 also of the so-called guano-biliary acid s which apparently belongs to 

 this order, nothing is known. 



Isolation. The common glycocholic acid is most conveniently 

 obtained by starting with Platner's bile, that has been prepared from 

 human bile or from that of the ox, as already described. 



Or, the following method may be employed (Bleibtreu) : Start- 

 ing with ox-bile the pigments are precipitated with uranium acetate ; 

 the bile acids remain in solution. In the nitrate glycocholic acid is 

 precipitated with chloride of iron ; the resulting iron compound is 

 decomposed by heating with ammonia, the hydroxide of iron is fil- 

 tered off, the nitrate acidified with hydrochloric acid and shaken 

 with ether ; the glycocholic acid separates out in crystalline form. 

 Or, to purify the substance further, the ammoniacal solution is neu- 

 tralized with acetic acid, the glycocholic acid precipitated with 

 uranium nitrate, and the precipitate decomposed by heating with 

 sodium phosphate solution. The resulting solution of the sodium 

 salt is acidified with hydrochloric acid and shaken with ether, when 

 the glycocholic acid separates out. 



Hyoglycocholic acid can be isolated from the bile of the pig by 

 first decolorizing with animal charcoal and then salting with sodium 

 sulphate in substance. The acid is thus precipitated, and can then 

 be filtered off. It is washed with a solution of the salt, dissolved in 

 water, and precipitated in the form of the free acid by means of 

 hydrochloric acid. 



Taurocholic Acid. Taurocholic acid, as has been stated, is the 

 only biliary acid that is found in the bile of the purely carnivor- 

 ous animals, but it also occurs in the bile of man and most herbiv- 

 orous animals. Among these, the sheep and goat are especially 

 noteworthy, as in these, like the pure carnivora, taurocholic acid 

 only is found. It is formed synthetically in the liver from taurin 

 and cholalic acid, and is accordingly resolved into its components 



