128 ANIMAL CHEMISTRY LECTURE YI. 







brated ' Traite de Cliimie Organique,' gave a very complete account 

 of the then known uric acid products, and, by dividing them into 

 two well-defined natural groups, simplified very greatly the con- 

 ception of their origins and metamorphoses. Among subsequent 

 workers, Strecker has added considerably to our knowledge ; and 

 Baeyer has increased the list of compounds by his discovery of 

 pseudo-uric acid, hydantoine, violantine, and the violuric and 

 barbituric acids, the last-named being a body of very great inte- 

 rest; while he has also thrown considerable light upon the nature of 

 the bodies previously discovered by Schlieper. Moreover, adopt- 

 ing Gerhardt's classification as a basis, and viewing both old and 

 new products from the extreme height of modern doctrine, he has 

 published by far the most complete and connected account of the 

 uric acid group of compounds which has hitherto been given to 

 the world. The scheme which I am about to bring under your 

 notice, and which, I think I may say, is even more comprehen- 

 sive, does not differ greatly from that of Baeyer in principle, and 

 is indebted very largely to him for its elaboration. I propose, 

 however, to differ from him in disregarding altogether the mole- 

 cular arrangement of the different compounds, preferring to limit 

 myself in this, as in previous lectures, simply to questions of 

 origin and relationship. 



(i 36.) I have already told you that the great majority of com- 

 plex organic bodies are built up of the residues of comparatively 

 simple molecules ; that hippuric acid, for instance, is constituted 

 of the residues of benzoic acid and glycocine, while tyrosine is 

 constituted of the residues of salicic acid and ethylamine the 

 glycocine and ethylamine themselves containing residues of am- 

 monia and of glycolic acid and alcohol respectively. Now, uric 

 acid is evidently built up in a similar manner, and contains the 

 residues of several constituent molecules. But a hitherto insupe- 

 rable difficulty in determining its exact mode of construction 

 arises from the circumstance of its never having been decomposed 

 into the actual molecules of which its constituent residues are the 

 representatives, but only into the oxidised, or rather dehydro- 

 genised, products of these molecules. Add to uric acid an atom 



