188 THE PROTEIN SUBSTANCES. 



cells appear in such places as were before endowed in a relatively poor 

 manner. As an example of this, the blood, in leucaemia, is extremely rich 

 in leucocytes. In such blood KOSSEL 1 found 1.04 p. m. purine bases, 

 against only traces in the normal blood. That these bases are also inter- 

 mediate steps in the formation of uric acid in the animal organism is 

 probable, and will be shown later (see Chapter XIV). 



Only a few of the purine bases have been found in the urine or in the 

 muscles. Only four bases xanthine, guanine, hypoxanthine, and ade- 

 nine have been obtained, thus far, as cleavage products of nucleins, 

 and these do not always have a primary origin. In regard to the purine 

 bodies from other substances we refer the reader to their respective 

 chapters. Only the above four bodies, the real nuclein bases, will be 

 considered at this time. 



Of these four bodies, xanthine and guanine form one special group 

 and hypoxanthine and adenine another. By the action of nitrous acid 

 guanine is converted into xanthine and adenine into hypoxanthine. 



C 5 H 4 N40.NH+HN0 2 = 



Guanine Xanthine 



Adenine Hypoxanthine 



Similar transformation, where xanthine and hypoxanthine are pro- 

 duced secondarily, may also occur in the hydrolysis of nucleic acids as 

 well as in putrefaction and by the action of special enzymes. The 

 researches of SCHITTENHELM, LEVENE, JONES, PARTRIDGE, WINTERNITZ, 

 and BURIAN have shown that in various organs deamination enzymes, 

 such as guanase and adenase, occur, which convert guanine and adenine 

 into xanthine and hypoxanthine respectively, and also oxidases which 

 oxidize hypoxanthine into xanthine and this then into uric acid. This 

 formation of uric acid from the purine bases, which will be discussed in 

 detail in a following chapter (XIV), is of very great interest. 



The nuclein bases form crystalline salts with mineral acids, which, 

 with the exception of the adenine salts, are decomposed by water. They 

 are easily dissolved by alkalies, while with ammonia their action is some- 

 what different. They are all precipitated from acid solution by phos- 

 photungstic acid; they also separate as silver compounds on addition 

 of ammonia and ammoniacal silver-nitrate solution. These precipitates 

 are soluble in boiling nitric acid of 1.1 specific gravity. All purine bodies 

 are also precipitated by FEHLING'S solution (see Chapter III) in the pres- 

 ence of a reducing substance such as hydroxylamine (DRECHSEL and 

 BALKE). Copper sulphate and sodium bisulphite may also be used to 



1 Zeitschr. f. physiol. Chem.. 7. 



