THE BILE. 149 



anhydride of glycocholic acid is precipitated in the form of oily 

 droplets, which subsequently tend to coalesce. This anhydride is 

 termed cholonic acid, and has the composition C^H^NOg. 



According to Michailoff, glycocholic acid when treated with con- 

 centrated sulphuric acid in the presence of acetic acid is said to yield 

 an orange color with a green fluorescence. On salting with ammo- 

 nium sulphate a precipitate is formed which in its reactions is 

 identical with biliverdin. Urobilin is said to remain in solution. 

 This observation is of special interest, as showing the possible rela- 

 tionship which may exist between the biliary acids and the bile- 

 pigments. We find, as a matter of fact, that an increase in the 

 production of bile-pigments on the part of the liver is associated 

 with a diminished formation of biliary acids. Others have con- 

 cluded from this observation that a connection between the produc- 

 tion of bile-acids and bile-pigments does not exist, and that the 

 origin of the two classes of substances must be referred to a separate 

 activity on the part of the hepatic cells. It appears to me, however, 

 that this inference is not altogether justifiable. 



Closely related to the common glycocholic acid is the so-called %o- 

 glycocholio 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 : 



naOs + 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,, 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. 



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- 



