556 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



except the nuclein from spermatozoa in which the acid combines with pro- 

 tamin. The simplest indication of the cleavage of nuclein (see Nuclein) on 

 chemical treatment, may be written as follows: 



Nuclein. 



Proteid. Nucleic acid. 



Phosphoric acid. Adenin. 



Guanin. 



Xanthin. 



Hypoxanthin. 



The idea that the purin bodies occurring in the urine of mammals are 

 the metabolic products of nuoleins, the uric acid being derived from the 

 oxidation of the bases, was made especially clear by the experiments of 

 Horbaczewski. 1 His statement that feeding nucleins increases the purin 

 bases and the uric acid in the urine has been frequently confirmed. He also 

 showed that if fresh spleen pulp, which contains no purin bodies, be per- 

 mitted to putrefy, the extract will contain xanthin and hypoxanthin, whereas 

 if the spleen pulp be shaken with the air uric acid is produced, being oxi- 

 dized from these bases. Spitzer 2 finds, if air be passed through spleen and 

 liver extracts digested at 40° with the exclusion of putrefaction, that uric 

 acid is produced. The nuclein bases formed decrease with the increase of 

 uric acid. Hypoxanthin and xanthin added to such digests are readily oxi- 

 dized to uric acid, as are adenin and guanin, although with greater difficulty. 

 Extracts of the kidney, pancreas, thymus, and blood have no such power. 

 Feeding uric acid and nuclein bases increases the amount of urea in the 

 urine. Minkowski 3 has proved that after feediug hypoxanthin uric acid 

 increases in the urine, showing its oxidation. Minkowski also showed after 

 feeding a man with thymus, the nuclein of which yields principally adenin 

 with some guanin, that the amount of uric acid was increased in the urine; 

 the same food fed to a dog increased the uric acid, and allantoin, an oxidation 

 product of uric acid, also appeared. Feeding adenin to a dog did not in- 

 crease the uric acid or allantoin excretion, but on autopsy of the dog there 

 was found a deposit of uric acid in the uriniferous tubules with indications 

 of inflammatory processes. This is the first known artificial production of a 

 deposition of uric acid. It would seem that the adenin in combination with 

 nucleic acid in thymus may be readily burned to uric acid in such a way 

 that it is readily excreted, whereas adenin itself behaves differently. Loewi 4 

 finds that the same amount of nuclei]] food fed to different people results in 

 tin <ame excretion of uric acid. He therefore concludes that all the purin 

 bodies liberated in metabolism are quantitatively eliminated. The analysis of 



1 Sitzungsberichte der Wiener Akademie der Wissenschaft, 1891, Bd. 100, Abth. iii. S. 13. 



2 Pjliiffer's Archiv, 1899, Bd. 76, S. 192. 



3 Archiv fur acper. Patholorjir umd I'lmrmakologie, 1898, Bd. 41, S. 375. 



4 Ibid., 1900,Bd. 44, S. 1. 



