SYNTHETIC PURIN FORMATION IN MAMMALS 157 



very evident that the problem cannot be regarded at present 

 as solved. 



It has been actually shown in Minkowski's laboratory 

 that, as previously suspected, besides the synthetic formation 

 in the avian body there is also an oxidation formation of 

 uric acid in small amounts in complete analogy to the process 

 in mammals. 



Synthetic Purin Formation in Mammals. There is no 

 evidence at all at present to indicate that uric acid is 

 synthetically produced in mammalian animals and man 

 along with its oxidative production, in analogy to the proc- 

 ess seen in birds, as was asserted by H. Wiener. 22 However, 

 there is no doubt as to the ability even of the mam- 

 malian body to construct purin complexes in prepara- 

 tion for their incorporation in the molecules of nucleinic 

 acid. The most important points in this connection have 

 been previously considered (Vol. I of this series, p. 129, 

 Chemistry of the Tissues). Proof is available not only in 

 case of the eggs of the silk moth and of the hen, the salmon 

 in starvation, but also in case of growing sucklings and of 

 rats fed upon purin-f ree diet, that the animal body is able to 

 construct de novo the bases necessary for purin formation 

 out of practically any components of the protein molecule; 

 and that it is not restricted exclusively to purin bases of 

 exogenous origin. 22a But no one knows just how this con- 

 struction takes place. It has not been successfully shown by 

 feeding experiments that transformation takes place of de- 



N C 



rivatives of the pyrimidin nucleus, 23 C C, (Vol. I of this 



N C 



22 R. Burian, Zeitschr. f. physiol. Chem., 43, 497, 1905; W. Pfeiffer (F. Hof- 

 meister's Lab., S'trassburg, and Quincke's Clinic, Kiel), Hofmeister's Beitr., 10, 

 324, 1907. 



22a E. V. McCollum (Wisconsin), Amer. Jour, of Physiol., 25, 120, 1909; 

 L. S. Fridericia (Copenhagen), Skandin. Arch. f. Physiol., 26, 1, 1912; cf. therein 

 Literature. 



23 L. B. Mendel and V. C. Myers (Yale Univ.), Amer. Jour, of Physiol., 26, 

 77, 1910. 



