URIC ACID AND THE PURINE BODIES 637 



From an examination of the structural formulas, it will be seen that 

 they are more or less related to purine (having one of the urea radicles 

 omitted), although it can scarcely be doubted that they exist as separate 

 constituents of the nucleic acid group in the animal body, and are not 

 derived from purine. They are primary products. 



The Chemical Nature of the Substances in Which Purine and 

 Pyrimicdne Bases Exist in the Animal Body. In general it may be said 

 that the amino purines adenine and guanine together with the 

 pyrimidine bases thymine and cytosine occur combined with phos- 

 phoric acid and a carbohydrate in the various nucleic acids, each of which 

 is again combined with some simple protein to form, nuclein, the essen- 

 tial constituent of the chromatin of the nucleus. One of the oxypurines, 

 hypoxanthine, may also exist combined with phosphoric acid and carbo- 

 hydrate to form a substance present in muscle and known as inosinic 

 acid. The general scheme of construction of a nucleic acid of animal 

 origin is illustrated in the following formula suggested by Levene and 

 Jacobs: 30 



HO 



O = PO C 6 H 10 O 4 C 5 H 4 N 5 O 



/ (hexose) (guanine group) 



</. 



HO | 



- \ i 



O = PO C 6 H S 2 C 5 H 5 N 2 2 



/ (hexose) (thymine group) 



HO 



O 

 HO 



\ 



O = PO C 6 H S O 2 C 4 H 4 N,0 



(hexose) (cytosine group) 



HO 



O 



Phosphoric acid \ 



groups O PO C H 10 O 4 C S H 4 N 5 



/ (hexose) (adenine group) 



HO 



According to this formula nucleic acid may be considered as a com- 

 pound of polyphosphoric acid, containing carbohydrate groups, which 

 serve to link the phosphoric acid molecules to those of purine or pyrimi- 

 dine. In nucleic acids of animal origin, such as the example given 

 above, the carbohydrate is a hexose, (i.e., contains 6 C-atoms), whereas 



