CHEMICAL BASIS OF THK ANIMAL BOPV. 175 



remembered that the latter are regarded by plant-pliysiologists as 

 products of the vegetable organism, and are thus found 

 chiftly in those parts of the plant which are on their way to re- 

 moval, viz. the bark, leaves, and seeds. 



Many nu-iubers of this ^nmp are both derivable from and con- 

 vertible into other members of the group by simple chemical 

 jiror.-sses, but this relationship of the one to the other will be 

 more fully appreciated by consideration of the properties and 

 reactions of the separate substances. Tlu-ir relationships to uric 

 ui.l and cai h other are in many cases indicated by comparison 

 of their formulae. 



1. Xanthin. C 5 H 4 N NH CH 



CO C NH 



\ 



N'H c = N 



|^ ^CO (Fischer) 1 . 



C = N 



First discovered in a urinary calculus, and called xanthic oxide. 

 M"iv ivivntly it has been found as a normal, though very scanty, 

 constitiifiit of urine, muscles, and several other tissues, such as 

 the. liver, spleen, thymus, brain-substance, &c. It occurs in larger 

 quantities, together with hypoxanthin, in 'extract of meat,' and 

 is also found in traces in vegetable tissues, lupins, malt-seed- 



Fi... U:i. XVMIIIN IMI.KM. III..HIDE, I'l" ->. X AM HIM NITRATE, 



C,I1,N,", HC1. (Kul.u.-.) c, II.N.o. -.IIXn s . (Kiihne.) 



lings, and tea. In nearly all cases it is accompanied by hypo- 

 xantliin. Tli<' amount which is present in any of the above 

 turaefl and fluids is so small that none of them, except perhaps 

 theextrart "f meat, affords a convenient source for its prepara- 

 tion. 2 To obtain it in quantity guanin is treated with nitrous 

 acid, 8 and the nitro-product thus obtained is reduced in amnionia- 

 cal -olution with ferrous sulphate. It may also be prepared 

 .ntiticiallv from hydrocyanic acid and water in presence of acetic 

 a.id. Wli.-n pun- it is a mlmirless powder, requiring about 

 14,000 parts of water for its solution at ordinary 



1 (i) far. d. d. chem. GweU. 1882, S. 453. (ii) Ann. d. Chem. u. Pharm. Bd 

 i \ \ 18821 v 



2 For it'fepamti.iii fn.m urine see Nenbauor, Zt.f.anal. Chem. IM vn. (1868), 



irt, ee St&deler, .!/. ' . 1'hnrm. !?.i axn 



(1860). \oubauer, Zt.f. anal. C 1 /,. m. IMf. u. (1863), S. 26, vi. (1867), S. :n. 



8 Fischer, loe. cil. (ii). 

 Gantier, Compt. Rend. T. 98 (1884), 1523. 



