166 PHYSIOLOGY OF PURIN METABOLISM 



statements of Ascoli and Izar 55 to the effect that uric acid 

 may reform after it has undergone a previous decomposi- 

 tion. These authors observed the disappearance of sodium 

 urate which had been added to hepatic pulp in the incubator 

 when a stream of air was conducted through it. When the 

 material was left in the incubator with air excluded it is 

 said reformation of the uric acid took place. Control ex- 

 periments are said to have shown that the newly formed uric 

 acid did not come from any cleavage of nucleins belonging 

 in the liver pulp, but from a real regeneration of the decom- 

 posed uric acid. From what has been said (vide supra) it 

 would be necessary to assume that in oxidation-destruction 

 of uric acid in liver extracts allantoin would be formed. That 

 this is the case has meanwhile recently been shown by 

 Fasiani, although he was unable to confirm the regeneration 

 of the uric acid. 56 The author prefers to postpone any 

 definite opinion upon the matter until the conclusion of 

 experiments now in course in his laboratory. 



Methylated Pur in Derivatives. Besides the typical purin 

 bases there is a series of methylated purin derivatives pres- 

 ent in small quantities in urine, which originate from the 

 caffein, theobromin and theophyllin of coffee and tea. Their 

 nature has been fully demonstrated, in the first place by 

 their synthetic production by Emil Fischer and, too, espe- 

 cially by the studies of Rost, Albanese, Bondzynski and 

 Gottlieb, Salomon, Kriiger, J. Schmid and Schittenhelm. 57 

 The schema below printed may serve to indicate their rela- 

 tion (in which, as in previous instances the writer has 

 omitted for brevity hydrogen atoms and double bindings) : 



" M. Ascoli and G. Izar, Zeitschr. f . physiol. Chem., 58, 529, 1909 ; G. Izar, 

 ibid., 65, 88, 1910. 



" Fasiani, Arch. Ital. de Biol., 57, 222, 1912. 



"Literature: A. Ellinger, Handb. d. Biochem., 3', 579-581, 1910; A. Schit- 

 tenhelm, ibid., 4', 525-528, 1910. 



