ALLANTOIN AS AN END-PRODUCT 159 



That this is really the expression of a physiological 

 process is evidenced directly by the fact that in the mammals 

 carefully studied from this point of view (dog, cat, rabbit, 

 hog, cow) excretion of uric acid and of the purin bases is 

 decidedly overshadowed by allantoin, as shown from obser- 

 vations of Schittenhelm, Abderhalden, Underbill, L. B. Men- 

 del and others. Parenterally introduced uric acid is com- 

 pletely excreted by dogs and rabbits, in by far the greater 

 proportion as allantoin, and only in minor amount as uric 

 acid. Nucleinic acid from thymus derivation, too, when in- 

 troduced with the food, according to Schittenhelm 27 under- 

 goes cleavage in the body of the dog in a way that the great 

 bulk (93-97 per cent.) of its purins appear as allantoin, and 

 only the small residual percentage is partitioned as uric acid 

 and purin bases. The author's pupil, W. Hirokawa, 28 ob- 

 tained similar figures when nucleinic acid was fed to dogs ; 

 although the purins did not appear in the urine entirely free 

 from residue. Likewise, too, in the pig 29 after adminis- 

 tration of nucleinic acid the purins for the most part appear 

 in the allantoin fraction. On the basis of these observations, 

 supplemented by numerous older findings bearing upon the 

 conversion of uric acid and nucleinic substances into allan- 

 toin, 30 Wiechowski has been thoroughly corroborated in 

 his statement that allantoin is to be regarded and accepted 

 as an end-product of uric acid metabolism, and that besides 

 allantoin no other products (neither oxalic acid, glycocoll nor 

 urea) of the intermediate uric acid metabolism are met in 

 mammalian animals. 



Further explanation is not necessary for appreciation of 

 the fact that allantoin, an end-product of the normal vital 

 catabolism of nucleoproteids and nucleinic acids, appears in 

 the catabolism of the same substances in case of intoxication 



37 A. Schittenhelm, Zeitschr. f . physiol. Chem., 62, 80, 1909. 



38 W. Hirokawa, Biochem. Zeitschr., 26, 441, 1910; under direction of 

 O. v. Furth. 



"A. Schittenhelm, Zeitschr. f. physiol. Chem., 66, 53, 1910. 

 M Salkowski, Minkowski, Th. Cohn, L. B. Mendel and others. 



