PURINS IN HUMAN METABOLISM 163 



To this Wiechowski makes adverse reply. He acknowl- 

 edges that the subcutaneous injection of uric acid severely 

 taxes the metabolism. It is not impossible that a toxic ac- 

 tion, which must be taken into consideration, but permitted 

 to proceed, may afford correct conclusions in animal ex- 

 perimentation; in no case, however, can the metabolic dis- 

 turbance produced explain why the greater part of uric acid 

 which has been parenterally introduced into a human being 

 is excreted unaltered. 



Schittenhelm's 41 finding, that experimentally introduced 

 allantoin is not affected in human metabolism, is an impor- 

 tant one. Were uric acid catabolized in man, as in animals, 

 in important degree into allantoin, we might expect that the 

 latter would appear in the urine ; but actually very small 

 amounts only of this substance occur normally therein. 42 



In harmony with earlier opinions of Otto Lowi 43 and of 

 Soetbeer and Ibrahim, 44 Wiechowski concludes that inter- 

 mediate uric acid is not broken down in man in any really im- 

 portant amount. "For this conclusion the individual con- 

 stancy of endogenous uric acid excretion is a favorable point. 

 For how else can this be explained if, as shown, the reality of 

 a so-called integrative factor of the amount decomposed is 

 not to be assumed. And the established difference between 

 the urine of mammals and of man on purin-free diet (in one 

 case a rich and individually constant daily allantoin elimina- 

 tion with very low uric acid elimination in the other a rich 

 and individually constant excretion of uric acid in the 

 twenty-four hours with mere traces of allantoin excretion) 

 may be looked upon as entirely satisfactory and logical evi- 

 dence of the inferred position of the human being in relation 

 to uric acid/' 45 Finally Wiechowski 45a comes to the point 



41 A. Schittenhelm and K. Wiener, Zeitschr. f. physiol. Chem., 63, 283, 1909. 

 42 K. Ascher (Prague), Biochem. Zeitschr., 26, 370, 1910. 



43 O. Lowi, Arch. f. exper. Pathol., 44, 22, 1900. 



44 F. Soetbeer and J. Ibrahim (Heidelberg), Zeitschr. f. physiol. Chem., 

 35, 1, 1902. 



40 W. Wiechowski, Arch, f . exper. Pathol., 60, 206, 1904. 

 45 a W. Wiechowski, Biochem. Zeitsch., 25, 445, 1910. 



