114 PHYSIOLOGY 



guanine (C 5 H 5 N 5 0). These substances, with the products of their 

 oxidation, xanthine, C 5 H 4 N 4 2 , hypoxanthine, C 5 H 4 N 4 0, have long 

 been known to be closely allied to uric acid, C 5 H 4 N 4 3 , but their true 

 relationships have only been thoroughly known since the researches of 

 Fischer on this group. According to Fischer they can be all regarded 

 as derivatives of the body purine, 



5 C NH 7 



II II >H 8 



SN_ 4 c N 9 r 



Each group in this purine ring is generally designated with a number 

 indicated in the structural formula, in order that it may be possible 

 to represent the position of any substituted groups in its derivatives. 

 Uric acid itself is 2-6-8-trioxypurine with the following formula : 



HN CO 



I I 

 OC C NH 



I II >0 



C NH X 



It can be synthetised by fusing together in a sealed tube trichloro- 

 lactamide and urea. Thus : 



NH 2 CONH 2 NH CO 



II II 



CO + CHOH + NH 2X = CO C-NH X + NH 4 C1. + 2HC1 



II >co I || .)co 



NH 2 CC1 3 NH/ NH C NH/ 



The relation of xanthine, hypoxanthine, guanine, and adenine to uric 

 acid is shown by the following formulae : 



Closely allied to this group of bodies are the chief constituents of tea, 



