426 THE METABOLISM OF THE PURIN BODIES 



cule being a body called an ureide, in this case dialuric acid, 

 thus : 



NH-CO 



/NH 9 HOOC\ / | 



CO X % X CHOH = CO CHOH + 2H 2 



\NH 2 HOOC/ \ 



NH-CO 

 (Urea) (Tartronic acid) (Dialuric acid] 



Dialuric acid then unites with a second urea molecule forming uric 

 acid, thus : 



NH-CO 



| NH-CO 



CO CHOH + H,N X | +2H 2 O 



| >CO - CO C - NH 



NH-CO H N/ \ || \CQ 



NH - C - NH/ 



(Dialuric acid) (Urea) (Uric acid) 



Wiener, therefore, thinks that all the above bodies which when 

 given per os under the conditions described above cause uric acid 

 to be excreted in excess must first of all become converted into 

 tartronic acid or into dialuric acid, before they form uric acid. 



Can similar bodies produce uric acid synthesis in mammals? 

 We have already incidentally mentioned that in mammals such a 

 synthetic process is improbable under normal conditions. If, 

 however, certain of these bodies, which exaggerate the synthesis in 

 birds, be administered to men, an increase, small indeed but still 

 perceptible, is seen in the uric acid excretion (Wiener) ; and since 

 there is reason to believe that lactic acid is produced as a bye- 

 product of metabolism in the tissues, a synthesis of uric acid in 

 mammals is quite conceivable. It is at present an open question 

 and requires further investigation. 1 



1 Wiener has tried to prove his contention of a synthesis existing in 

 mammals by an experiment in which he perfused the liver of oxen with 

 a substance contained in the alcoholic extract of various organs (and which 

 contained no purin bodies), and found a production of uric acid. If synthesis of 

 uric acid exists at all under normal conditions in mammals, or if it only obtains 

 where an excess of the carbon residue is present, is undetermined. The latter is 

 the view of Burian and Schur, and is the more probable state of affairs. Burian 

 has further shown that tartronic and dialuric acids have the power of accele- 

 rating the action of xanthin-oxydase, which would account for the increase of 

 uric acid in the ox's liver when the bodies are perfused through it, 



