410 THE METABOLISM OF THE PURIN BODIES 



the increase in the purin excretion which follows purin ingestion 

 really is due to some of the ingested purin reappearing in the 

 urine, or whether it may not be the result of a stimulating 

 effect which exogenous purins might conceivably have on the pro- 

 duction of purins in the tissues in other words, on the endogenous 

 production of purins. The former explanation is made probable 

 by the fact that in dogs the subcutaneous injection of a solution 

 of uric acid and feeding with thymus gland or with hypoxanthin, 

 all increase the purin excretion to about the same extent. 1 The 

 following table demonstrates this : 



TABLE V 



Average purin-JV in dog's } 

 urine on an endogenous > 

 diet ) 



Increase of purin-AT after 

 feeding with 0'4 grin. 

 purin-iV in thymus 



Increase in purin- N after 

 subcutaneously injecting 

 0'4 grin, uric agid-JV 



Increase in purin-JV after 

 feeding with 0*4 grm. 

 hypoxanthin-^V 



0-0156 grm, 



Q'0157 grm. = 3'9 % of the purin administered. 



0-0160 grin. = 4 



0-0185 grm. = 4-6 



In man, too, the addition of hypoxanthin to the diet raises 

 the excretion of uric acid but has no influence on that of 

 phosphoric acid (Krueger and Schmidt, vide 20 ). If the higher 

 purin excretion, in this case, had been due to an increased 

 endogenous production, the phosphate excretion would probably 

 have been raised as ^well as that of the purin bodies, since 

 phosphoric acid is also an ultimate metabolic product of nuclein, 

 and nuclein is, in part at least, a source of endogenous purins. 

 There can be no doubt, therefore, that a portion of administered 

 purin passes unchanged into the urine. 2 



The above table furnishes us also with data from which our 



1 The difference in the increase of exogenous purins following ingestion of 

 amido- and oxy-purins is not evident in the case of the dog. 



2 A point of difference between the dog and man must be noted here, viz. 

 that thymus purins are excreted in the dog's urine to the same extent as 

 xanthin, wheraas in tise case of man this is not the case. 



