136 THE UKINE. 



and creatinin: 



HN CO 



H 3 CN CH 2 



are closely related, the latter being derived from the former 

 by taking away one molecule of water, and can be changed 

 back into creatin by adding the water again. 



The nuclein bases, also called purin bases, xanthin 

 bases and alloxuric bases, guanin (C 5 H 5 N 5 0), hypoxanthin 

 (C 5 H 4 N" 4 0), and xanthin (C 5 H 4 N 4 2 ) are similar in their 

 properties and related to uric acid (C 5 H 4 N 4 3 ). They 

 are derivatives of the hypothetical nucleus, purin: 



(6) 

 (1)N= CH 



I (7) 

 (2 ) HC (5) C NH 



II II > CH (8) 

 (3)N C- N 



(4) (9) 



They are formed by the addition to, or substitution in 

 this of oxygen or organic radicals, the position being in- 

 dicated by the figures. Thus guanin is 2-amino-6-oxy- 

 purin. Hypoxanthin is 6-oxypurin; xanthin, 2-6-dioxy- 

 purin and uric acid, 2-6-8-trioxypurin. They occur partly 

 free in the muscular tissue and partly united with phos- 

 phoric acid and albuminous substances in the form of 

 nucleins. All these soluble compounds are found, natur- 

 ally, in the various meat-extracts, which are used in foods. 

 They are probably formed in the body by the decompo- 

 sition of the albuminous materials. When taken as a food, 



