414 THE METABOLISM OF THE PURIN BODIES 



amount of benzole acid be given to rabbits so that an excess is 

 present in the tissues, the hippuric acid excretion will become 

 maximal and of constant amount; all the available glycin in the 

 organism being used up to form hippuric acid. In such a con- 

 dition any added glycin, by uniting with the excess of benzoic 

 acid, will at once raise the hippuric acid excretion. By feeding 

 such rabbits with uric acid Wiener obtained an increase in the 

 hippuric acid excretion, showing plainly that glycin had been 

 formed in the organism. Wiener has confirmed this result by 

 finding that glycin is formed when uric acid and a saline extract 

 of ox's kidneys are incubated for some time. As we shall see 

 later, the kidneys are the site of uric acid destruction in herbivora. 

 Glycin, then, is undoubtedly a decomposition product of purin 

 disruption in lierliwra, and is most probably also so in man, 

 although, in this case, experiments similar to those of Weiner on 

 rabbits have not, so far as I am aware, been performed. 



With regard to cdlantoin, there seemed for long to be un- 

 doubted evidence of its being the chief intermediate product of 

 uric acid destruction in the body. Salkowski found it present in 

 considerable amount in the urine of dogs to which large amounts 

 of uric acid had been given, and the same result has been obtained 

 in similar experiments on cats ( 17 ). Thus Mendel, Underbill, and 

 White have shown that in whatever way nucleic acid is adminis- 

 tered to cats and dogs it causes a very distinct increase in the 

 allantoin excretion, and that intravenous injection of lithium urate 

 also raises the allantoin excretion. Allantoin has also been found 

 present, under normal conditions, in the urine of several animals, 

 but never, in any amount at least, in the urine of man, even after 

 copious purin ingestion. Nor has it been observed in the urine of 

 herbivorous animals under similar conditions. These results ( 3 ) 

 seem to show that the uric acid produced by purin decomposition 

 in the body is oxidised only as far as allantoin in dogs and cats, 

 but that, in man, the allantoin is further converted into urea. It 

 was further observed (by Minkowski) that in feeding dogs with 

 allantoin all of it passed unchanged into the urine, whereas in man 

 only one -fourth could be thus recovered. This being so, one could 

 expect, were allantoin really produced in the tissues, its presence 

 in considerable amount as a normal constituent of dog's urine, 

 which it is not ; and, in human urine, we would expect its appear- 

 ance after extensive purin katabolism, which has also never been 



