THE METABOLISM OF THE PURIN BODIES 417 



production of (endogenous) purins had been raised by the opera- 

 tion, not their destruction diminished. That such is improbable, 

 however, was shown by the total N-excretion (which is a measure 

 of tissue break- down) remaining constant. 



By the injection of oil into the lungs, and by poisoning 

 with hydrazine sulphate ( 20 ), allantoin makes its appearance in 

 considerable amount in the urine of dogs fed meanwhile on a 

 purin-free diet. Allantoin is a decomposition product of uric 

 acid in dogs. In both these experiments, the endogenous pro- 

 duction of purins must undoubtedly have been raised, and the 

 increased amount further destroyed, and excreted as allantoin. 

 Neither of the two latter experiments furnishes us, however, with 

 absolute proof, for it is possible though in view of Mendel's recent 

 work not probable that the allantoin might be derived from 

 something other than a purin substance. 



Burian and Schur ( 10 ) have recently removed all doubt of the 

 intermediary nature both of exogenous and endogenous purins. 

 Briefly, their experiments are as follows : The kidneys were excised 

 in several dogs, of whom some were previously fed with purin- 

 containing food, and others with purin - free. After periods 

 varying from one to three days, the dogs were killed and the 

 blocd carefully examined for uric acid. In no case, even where 

 large quantities of purin had been contained in the diet, was the 

 minutest trace of uric acid found present in the blood. Two 

 interpretations of this result are possible: (1) that uric acid be- 

 comes entirely destroyed somewhere in the body, unless some 

 of it be drained off in the kidneys before it is destroyed (i.e. 

 that Hoppe-Seyler's hypothesis is correct) ; (2) that the endogenous 

 uric acid is formed in the kidneys themselves from some non- 

 purin precursors, the exogenous portion being, however, capable 

 of destruction in the body (i.e. that Garrod's hypothesis is correct). 

 Excision of the kidneys, according to Garrod's hypothesis, would 

 mean want of formation of endogenous purins, and complete 

 destruction of the exogenous, because of their repeated circula- 

 tion through the destructive organs. 



To ascertain which of these explanations is the correct one it 

 was necessary to remove from the circulation not only the kidneys 

 but also the purin-destructive organ or organs. If, then, on a 

 purin-free diet, purins should accumulate in the blood, the kidneys 

 could not be the site of formation of endogenous purins. 



2D 



