248 LECTURE XI. 



conjugation of glycocoll with benzole acid can be accomplished without 

 the direct use of organs or cells. 



As regards the place where the hippuric acid is formed, it is to be noted 

 that what has been said applies only to dogs. Frogs produce hippuric 

 acid even after the extirpation of the kidneys. Salomon l also observed 

 hippuric acid in large amount after the administration of benzoic acid to 

 a rabbit whose kidneys had been removed. It is possible that the syn- 

 thesis of hippuric acid is more localized in the carnivora than it is with the 

 herbivora, because the formation of hippuric acid by the former under 

 normal conditions is only very small in amount. The quantity of hippuric 

 acid daily excreted by human beings under an ordinary diet is about 0.7 

 gram. It may be increased to more than 2 grams by a liberal diet of 

 vegetables or fruit. 



Glycocoll not only participates in the production of hippuric acid and 

 of the other artificially introduced products just mentioned, but is also a 

 component of glycocholic acid and glycocholeic acid. Both are decom- 

 posed, in the same manner as is hippuric acid, by boiling with acids or 

 alkalies into glycocoll, cholic acid, or choleic acid, respectively. These 

 last two acids are both found as constituents of the bile. 



Besides these, there is another acid containing sulphur called tauro- 

 cholic acid which is found in the bile of most animals, and is likewise 

 related to one of the albumin cleavage-products; i.e. to cystine. When 

 taurocholic acid is heated with acids or alkalies, it is decomposed into 

 taurine and cholic acid. The relations of taurine, which is an amino-ethyl- 

 sulphonic acid, to cystine and cysteine, are evident from the following 

 formulae : 



CH 2 SH CH 2 . S0 2 OH CH 2 . SO 2 . OH 



CH . NH 2 CH . NH 2 CH 2 . NH 2 



C00 COOH ^ ^ 



Cysteine Cysteinic acid Taurine 



Friedmann has succeeded, as previously mentioned, in converting 

 cysteine into cysteinic acid, and this into taurine. Shortly after the chemi- 

 cal relations between these compounds had been settled, experiments with 

 animals also indicated the probable derivation of taurine from cysteine. 

 W. v. Bergmann 2 fed dogs, in which he had made a complete biliary 

 fistula, with cysteine, and estimated the amount of taurocholic acid 

 separating out with the bile. He could not detect any increase in the 

 sulphur content of the bile in these experiments, but did notice such 



1 Z. physiol. Chem. 3, 365 (1879). 



2 Hofmeister's Beitr. 4, 132 (1903). 



