TAUROCHOLIC ACID. 231 



the most part only gradual, and are inapplicable as tests to enable 

 us to distinguish between small quantities of these acids. 



Physiological Relations. 



This acid has hitherto only been found in the bile of the pig, 

 where it exists in combination with soda, potash, and a little 

 ammonia. Our remarks on the origin and uses of glycocholic 

 acid are equally applicable to hyocholic acid. 



TAUROCHOLIC ACID. 

 Chemical Relations. 



Properties. This acid, which has also been named choleic acid> 

 and was formerly known as bilin, has not yet been obtained in a 

 state of perfect purity, that is to say, free from glycocholic acid ; 

 it cannot be obtained in a crystalline state, and it is more soluble 

 in water than glycocholic acid, while its acid properties are far 

 weaker. It dissolves fats, fatty acids, and cholesterin in large 

 quantities, and is thus the cause why glycocholic acid is not precipi- 

 tated from fresh ox-bile by acetic or the mineral acids. On expo- 

 sure to the air, as well as on evaporating a solution of the free 

 acid, decomposition ensues. When boiled with mineral acids it 

 becomes resolved into taurine and choloidic acid ; when boiled with 

 alkalies, into taurine, and cholic acid ; and when treated with sul- 

 phuric acid and sugar, it gives the same reaction as the other essen- 

 tial acids of the bile. The characters of its salts are, however, very 

 distinct from those of the other biliary acids. 



Composition. As this acid, like glycocholic acid, becomes 

 resolved, when acted on by mineral acids and by alkalies, into cho- 

 loidic or cholic acid, while in place of glycine it yields taurine, 

 Strecker,* to whom we are especially indebted for our know- 

 ledge of this acid and of its properties, correctly argues that 

 its composition is perfectly analogous with that of glycocholic 

 acid, the only difference being that the adjunct in this case is 

 taurine. Abstracting from the formula for taurine 1 atom of 

 water, he assumes that the empirical formula of this acid 

 = C 52 H 45 NS 2i4> and the rational formula^ C 4 H 6 NS 2 O 5 .C 48 H 39 O 9 . 

 We must therefore regard taurocholic acid as containing an adjunct 

 rich in sulphur, which, on its separation from the cholic acid, 



* Ann. d. Ch. u. Plmnn. Bd. 66, S. 43-61. 



