398 THE METABOLISM OF THE PURIN BODIES 



the amido-purins which exist in nuclein directly into uric 

 acid ; and yet, as we have seen above, nuclein undoubtedly 

 is an important mother substance of uric acid in extracts 

 of spleen and liver. It will be remembered that guanin is 

 amido-xanthin and adenin amido-hypoxanthin that is to say, 

 that by the removal of an amido group (NH 2 ) the transforma- 

 tion into the corresponding oxy-purin would occur. Jones ( 36 ) 

 and his co-workers and others have shown that the spleen and 

 liver of oxen possess another ferment guanase or adenase 

 which effects this removal of the amido group. 



The process of uric acid formation from nuclein entails, there- 

 fore, first of all a decomposition of the nuclein whereby, among 

 other things, amido-purins are produced ; a denitrification of these 

 amido-purins by guanase (and adenase) ; and then an oxidation of 

 the resulting oxy-purins into uric acid by means of xanthin-oxydase. 



These laboratory experiments undoubtedly prove that oxy- 

 purins can be derived from some group present in nuclein. 



With regard to the evidence that feeding with nuclein influences 

 the amount of urinary purins, Horbaczewski added 5 grm. of 

 nuclein prepared from spleen pulp to the diet of a man and 

 found an increase of 0'28 grm. in the urinary uric acid. Various 

 observers confirmed Horbaczewski in this result, and showed further 

 that all nuclein containing food-stuffs influenced the uric acid 

 excretion according to the amount and nature of the nuclein 

 which they contained }- 



In connection with the effect of nuclein feeding, our next 

 inquiry is whether or not the purin substances which the nuclein 

 contains can, when given in an uncombined state in the diet, 

 influence the purin excretion in tlie same way as nuclein itself 

 does ? The chemical structure of nuclein is demonstrated b}^ the 

 following scheme : 



1 These researches concerned almost without exception the uric acid excre- 

 tion ; the coincident behaviour of the other urinary purins was not, for want of 

 reliable methods, clearly demonstrated. Horbaczewski explained the results 

 which followed nuclein feeding by supposing that an excessive destruction of 

 leucocytes was produced, and that it was from the liberated nuclein of these 

 and not from the nuclein ingested, that the uric acid was derived. That such an 

 explanation could not hold was shown by Weintraud ( 7 ), who found that a thymus 

 diet did not cause any greater an increase in the number of leucocytes in the 

 blood than an ordinary diet did, but, nevertheless, increased the uric acid 

 excretion to a much greater extent. Weintraud therefore concluded that the 

 administered nuclein itself furnished tlie urinary purin. 



