154 PHYSIOLOGY OF PURIN METABOLISM 



considering the chemistry of muscular tissue (v. Vol. I of 

 this series, p. 159, Chemistry of the Tissues). It cannot be 

 doubted that muscular activity has a part in the formation of 

 the endogenous urinary purins. The fact, however, that 

 Schittenhelm 14 has found no striking reduction of the 

 endogenous amount in human beings with well marked mus- 

 cular atiophy would, however, contradict the idea that the 

 bulk of these substances originates in muscle tissue. Siven, 

 too, failed to recognize any characteristic influence of free 

 muscular movements upon the endogenous purin metabolism 

 in man 15 ; while Groudberg invariably found the uric acid 

 increased in starving rabbits after muscular spasms pro- 

 duced by faradism. 16 Finally it should be noted that mus- 

 cular involvement in processes concerned with heat regula- 

 tion is apparently more likely to influence the purin 

 excretion than voluntary contractions. The increased uric 

 acid excretion of fever and its nocturnal diminution are 

 perhaps related to the same type of processes. 17 



Synthetic Formation of Uric Acid in Birds and Reptiles. 

 Being in some measure satisfied of the production of uric 

 acid through processes of oxidation from nucleins, attention 

 should be directed to the synthetic production of uric acid. 18 

 It is known that the major portion of the nitrogen, which in 

 mammals, amphibians and fish is excreted as urea, is repre- 

 sented in birds, reptiles and also in many invertebrates 19 by 

 uric acid, which is produced in them synthetically. What is 

 known of the mechanism of this process ? 



"A. Schittenhelm, Handb. d. Biochem., 4' 521, 1910. 



15 V. O. given, 1. c. 



18 A. Goudberg (Hamburg), Zeitschr. f. Neurol. u. Psych., 8, 487, 1912. 



17 E. P. Cathcart, J. B. Leathes, E. L. Kennaway, cited by A. Ellinger, 

 Handb. d. Biochem., 4', 576, 1910. 



18 Literature upon the Synthesis of Uric Acid: H. Wiener, Ergebn. d. 

 Physiol., 1, 606-615, 1902; A. Magnus-Levy, v. Noorden's Handb., 1, 126-129, 

 1906; A. Schittenhelm, Handb. d. Biochem., 4', 522-525, 1910. 



"Of. O. v. Fttrth, Vergl. chem. Physiol. d. niederen Tiere, pp. 258-303, 

 Jena, 1903. 



