CRYSTAL^IZABLE NITROGENOUS MATTERS. 109 



neutral and tribasic lead acetates. Its alcoholic solution rotates the 

 plane of polarization toward the right 25.7. 



6. Sodimn Taurocholate, C^ 



This substance, the second characteristic ingredient of the bile, is 

 similar in many respects to the foregoing. Its organic acid, tauro- 

 cholic acid (C 26 H 45 NSO 7 ), is distinguished by containing an atom of 

 sulphur, owing perhaps to its derivation from albuminous matters. 

 If so, glycocholic acid must represent a product of further alteration, 

 in which sulphur, hydrogen, and oxygen are given up in such pro- 

 portions that the products of elimination are water and sulphur, as 

 follows : 



Taurocholic acid. Glycocholic acid. 



C a HNSO T H 2 S = a 6 H 43 N0 6 . 



By boiling with dilute acids or alkalies, or even with water, as well 

 as under the influence of putrefaction, taurocholic acid is decomposed 

 with the formation of two other bodies, namely, taurine (C 2 H 7 NSO 3 ), 

 a neutral nitrogenous substance, containing the sulphur, so called 

 because first discovered in bullock's bile, and cholic acid (C^H^Os), 

 the same body produced by a similar process from glycocholic acid. 

 The change takes place with the assumption of the elements of water, 

 as follows : 



Taurocholic acid. Taurine. Cholic acid. 



CaeH^NSO, -f H 2 O = C 8 H 7 NSO 8 -f C, 4 H 40 O 3 . 



Sodium taurocholate, like the preceding salt, is soluble in water 

 and in alcohol, and insoluble in ether. It is extracted from the bile 

 by a process similar to that already described, and, after precipita- 

 tion by ether, crystallizes in slender needles, much like those of the 

 glycocholate. It may be distinguished from the last-named substance 

 by its reaction with the salts of lead, not being precipitated from its 

 watery solution by the neutral, but only by the tribasic acetate. If 

 a watery solution, therefore, containing both biliary salts be precipi- 

 tated by neutral lead acetate, the filtered fluid will contain the tauro- 

 cholate alone. In alcoholic solution it rotates the plane of polarization 

 toward the right 24.5. With the exception of glucose, lactose and 

 glycogen, the biliary salts are the only substances known in the animal 

 body which exert a right-handed rotation on polarized light. 



The proportion in quantity of the two biliary salts varies somewhat 

 in different cases. Generally the glycocholate may be .said to prepon- 

 derate in the bile of ruminant animals, taurocholate in that of the 

 carnivora. In dog's and cat's bile, the taurocholate exists alone. In 

 human bile both substances may be present, sometimes one being more 

 abundant, sometimes the other ; according to some writers the tauro- 

 cholate existing alone or in larger proportion (Gorup-Besanez, Hoppe- 

 Seyler, Robin, Hardy), according to others the glycocholate (Bischoff, 

 Lessen, Ranke). In the observations of Jacobsen,* on a case of biliary 



* Revue des Sciences Medicales, Paris, 1874, vol. iii., p. 85. 



