140 ANIMAL CHEMISTRY LECTURE VI. 



in larger quantity by treating guanine with nitrous acid, accord- 

 ing to the general method adopted for converting amidated into 

 hydrated bodies, thus : 



Guanine Nitrous Xanthine 



C 5 N 4 H 3 (H a N)O + (HO)NO = C 5 N 4 H 3 (HO)0 + N, + H 4 0. 



That the guanine extracted from guano is a constituent of the 

 birds' excrement as voided, and not a product of decomposition, 

 is rendered probable by its occurrence under other circumstances. 

 Thus it forms the chief portion of the excrement of the garden 

 spider, has been recognised by Scheerer in the pancreas of the 

 horse, and is occasionally met with in human urine. 



(147.) We have now only left for consideration the pseudo- 

 uric and uroxanic acids, which we may regard as terms in the 

 following series : 



C 5 N 4 H 4 3 Uric. 



C 5 N 4 H 4 3 + H,0 = C 5 N 4 H 6 4 Pseudo-uric. 

 C 5 N 4 H 4 3 + 2 H 2 = C 5 N 4 H 8 5 

 C 5 N 4 H 4 3 + 3 H 3 = C 5 N 4 H 10 6 Uroxanic. 

 C 5 N 4 H 4 3 + 4H<0 = C 3 H 4 5 Tartronic * 2CN a H 4 Urea ? 



Pseudo-uric acid is a recent discovery of Baeyer's. It has 

 not actually been produced by the direct or indirect hydration of 

 uric acid, but only by the combination of cyanic acid vapour 

 with uramile or amido-barbituric acid. Just, in fact, as cyanic 

 acid converts ammonia into anomalous cyanate of ammonia or 

 urea, so does it convert the residue of ammonia contained in ura- 

 mile into a residue of urea, thereby changing the amido-monureide 

 into a simple diureide, thus : 



Uramile Cyanic acid Pseudo-uric 



C 4 N a H 3 (NH a )0 3 + CNHO = C 4 N,H 3 (CN a H 3 0)0 3 or C 5 N 4 H 6 4 . 



Pseudo-uric acid occurs as a white crystalline almost insoluble 

 powder. Hitherto it has not proved dehydrateable into uric acid ; 

 but by dehydrogenation, in presence of water, it behaves like 

 uric acid, breaking up into alloxan and urea. The compound 

 C 5 N 4 Hs0 5 is unknown, while uroxanic acid C 5 N 4 H 10 06, is 



