18 WILLIAM M. HAMLET. 



but the most complete demonstration of the structure of uric acid 

 is given us by the brilliant researches of Fischer. 1 He formulates 

 a framework thus : — 



,N=C 6 



I I 



2 C C 6 -N» 



II II >o 8 

 3 N-C 4 -Nf~ 



Filling up the available hydrogen positions, a compound is 

 represented which has actually been obtained, called by Fischer, 

 purine, (purum uricum): 



N— OH 



I I H 

 HC C— N^ 1 



I I >H 



N— C— N^ 



Hypoxanthine is 6 — oxypurine, and Xanthine is 2 : 6 — dioxy- 

 purine. Extending the oxygen positions to 2:6:8 we get 

 trioxypurine or uric acid : 



HN- CO 



I I H 

 00 C— N^ 



| | ^COH 



HN— C— N^ 



Placing two methyl radicles in the third and seventh positions we 



have '6 : 7 — dimethylxanthine which is the alkaloid — theobromine. 



The addition of a third methyl radicle formulates the composition 



of caffeine, the alkaloid present in tea and coffee, and which is 



1:3: 7 — trimethylxanthine — 



CH 3 



N CO 



CO C— NX^ 3 



I I >H 



N C— N^ 



CH 3 



What may be the structure of the globulins, the albumoses, 



hetero- and deutero-, the peptones, and that family of compounds 



1 Nature, Vol. lxi., p. 187. 



