162 PHYSIOLOGY OF PURIN METABOLISM 



findings constitutes a valuable scientific contribution to our 

 knowledge of the fate of uric acid in human beings. ' ' 



Fate of Experimentally Introduced Purins in Human 

 Metabolism. Another point of considerable importance is 

 the fate of artificially introduced uric acid in the human 

 metabolism. After feeding nucleinic acid to human be- 

 ings Schittenhelm, Brugsch and Frank have recovered as 

 a rule the greater part of the purin base nitrogen in the urea 

 fraction, a smaller portion in the uric acid fraction and only a 

 very small proportion as nitrogen of the purin bases. 38 Al- 

 lantoin which predominates in metabolism in animals is of 

 little importance here, and is found only in very small 

 amounts in the human urine. However, according to Wie- 

 chowski's results, uric acid introduced subcutaneously is 

 recovered for much the most part as such (up to 90 per cent.) 

 in the urine. 



There is a difference of opinion as to the importance of 

 this last result, between Wiechowski on the one hand, and 

 Brugsch and Schittenhelm on the other. Schittenhelm be- 

 lieves that because of its toxicity subcutaneous injections of 

 uric acid are not suited for conclusions with reference to 

 normal metabolic processes, and thinks it certain that uric 

 acid is in some proportion further catabolized in human me- 

 tabolism, with production of urea. 39 This view agrees with 

 that of Burian, who assumes that of the uric acid which 

 enters the circulation from without or which is produced in 

 the body by the breaking down of the nucleins, in man al- 

 ways about half is destroyed and only the other half is 

 excreted unchanged; for which reason he multiplies the 

 amount of excreted uric acid by the "integrative factor 2" 

 in order to obtain the total uric acid which entered the cir- 

 culation in the course of a day upon purin-free diet. 40 



M R. H. Plimmer, M. Dick and C. C. Lieb, Jour, of Physiol., 30, 98, 1909. 



"A. Schittenhelm, Handb. d. Biochem., 4', 516, 1910; cf. also L. B. Mendel 

 and J. F. Lyman (Yale Univ.), Jour, of Biol. Chem., 8, 115, 1910. 



40 R. Burian, Med. Klinik, 1905, No. 6, and 1906, Nos. 19-21. Consult in 

 these and in the contributions of R. Burian and H. Schur the Literature. 



