442 HIPPURIC ACID. [BOOK n. 



benzole acid. Glycin must therefore be present in the kidney or 

 liver, and its presence in the liver is further shewn by the formation 

 of glycocholic acid from cholalic acid. But singularly enough, glycin, 

 though a common product of the decomposition of proteid and 

 gelatiniferous substances, has hitherto not been found as such in 

 any part of the living body. 



Of the meaning of the appearance in the tissues of such bodies 

 as xanthin, &c., and of the exact nature of the metabolism which 

 they undergo, we know nothing. We cannot say whether they are 

 simply the accidental bye-products of nitrogenous metabolism, the 

 result of imperfect chemical machinery ; or whether they, though 

 small in quantity, serve some special ends in the economy. 



