CH KM ISTKY OF TIIK I. K I' CO M AINES. 



319 



hypoxanthinc, and cannot be? said to be tin- result of direct 

 experimental evidence. 



NH NH N==C Nil N=C NH 



N = C NH 

 CO 



NH C C=NH 



II I 

 CH NH 



GlTANINK. 



C 5 H 5 N 5 



N=C 

 CH 



NH 



N C C=NH 



II I 

 CH NH 



APKNINK. 



C 8 H 5 N 5 . 



HETEROXANTHINE, C 6 H 6 N 4 2 , is a now base which was 

 isolated from tlie urine in 1884 by SALOMON. In its 

 eompontion it is niethvl-xanthine, and is intermediate 



l)i 'tween xanthine and ]>araxanthine or dimethyl-xanthine. 

 It occurs in the urine of man and of the do in about the 

 same amount as para.xanthine, and the method for its isola- 

 tion will be found under the description of that base. It 

 is a remarkable fact that this base occurs in dog's urine 

 unaccompanied by parazanthine, and the same seems to 

 hold true for the urine of lcu< ocytlwmic jK'rsons. SALOMON 

 examined the liver and muscles of a dog, but was unable 

 to obtain any hctcroxanthine or paraxanthine, and the total 

 amount of .xanthine liodics pn sent was about normal. 

 Hence, he is inclined to think that these two bases may 

 |K>"iMy have their origin in the kidney. Unlike the other 

 xanthine liodics, h< teroxanthinc has not as yet Ixrn isolated 



