412 THE METABOLISM OF THE PURIN BODIES 



Similar experiments on herbivorous animals yield quite a 

 different integral factor. For example, in the rabbit, subcutaneous 

 injection of hypoxanthin or of uric acid causes an increase of 

 purin-^ excretion amounting to 17 '1-1 7 '7 per cent, of the 

 injected purin-^V. The integral factor in rabbits is therefore 6. 



To prove that the integral factor is the same for exogenous and 

 endogenous purins in the case of man it is, of course, impracticable 

 to perform all the injection experiments which have been practised 

 on dogs. Several such experiments have, however, been performed, 

 and, so far, they have yielded positive results. Schur, for example, 

 injected subcutaneously into himself 1 grm. of uric acid, in sterile 

 alkaline solution, and found an increase in urinary uric acid 

 amounting to 49 '85 per cent, of the injected uric acid. In a second 

 experiment 47*95 per cent, was recovered. We have already 

 seen that, in man, feeding with xanthin or hypoxanthin raises 

 the purin excretion to a similar extent, viz. 50 per cent. 1 That 

 these two modes of purin assimilation should raise the urinary 

 purins to an equal extent renders improbable any supposed influ- 

 ence the exogenous purins might conceivably have on the liberation 

 of endogenous purins, for it is unlikely that both modes would effect 

 the metabolism of the latter just to the same extent. The integral 

 factor for man, then, is 2. 



What becomes of that portion of food purin which disappears in 

 its passage through the organism? 



There are two possible answers to this question. It might be 

 stored up somewhere in the organism or it might be decomposed, 

 the purin ring being ruptured and excreted as something else. The 

 former possibility, that uric acid may be stored up somewhere in 

 the tissues, has been expounded as the true state of affairs mainly 

 by Haig ( 32 ) ; but, despite the large number of observations which 

 he has recorded in support of this view, it is not generally 

 accepted. It is disproved by the following, among other experi- 

 ments : if uric acid be injected subcutaneously into a dog, one- 

 twentieth part of it reappears as such in the urine ; according to 



1 This average (50 per cent.) for purins which reappear in urine in man is only 

 applicable to healthy individuals with full absorption, since, if absorption be 

 disturbed, the purins may pass into the fasces (Walker Hall). The purins of 

 meat are readily absorbed, whereas thymus, guanin, and nucleic acid are apt to 

 raise the purin percentage in the fasces. On an ordinary diet the purins of the 

 fasces amount to about '03-'OG grm. N in the twenty-four hours. 



