170 BASIC BODIES. 



physiological point of view, it approximates to urea, guanine, and 

 cystine. 



Preparation. Urinary calculi, in which this body occurs, are 

 dissolved in a solution of potash, and the xanthine is precipitated 

 from the filtered fluid by carbonic acid. 



Tests. From the circumstances under which it occurs, this 

 body can only be confounded with uric acid or cystine ; under the 

 microscope it may, however, be readily distinguished from them 

 by its amorphous condition. It differs chemically from uric acid, 

 firstly, in its ready solubility in ammonia, (hence it is not precipi- 

 tated from its potash-solution, like uric acid, by hydrochlorate of 

 ammonia;) secondly, in its being separated from its potash- 

 solution by carbonic acid, as a precipitate, free from the alkali ; 

 thirdly, in its dissolving in nitric acid without effervescence, and 

 on evaporation, leaving a (not red, but) yellow mass, which does not 

 become red on the addition of ammonia. It differs from cystine, 

 not only in its amorphism, but also in its insolubility in hydro 

 chloric and oxalic acids. 



Physiological Relations. 



Occurrence. This body was discovered in a urinary calculus 

 by Marcet, who, from its behaviour with nitric acid, gave it the 

 name of xanthic oxide. It has only been found once since, by 

 Stromeyer, in a large calculus removed from a child ; and it was 

 from this source that both Liebig and Wohler, and Unger, obtained 

 the materials for their analyses. Jackson* thought that he had 

 found it in a specimen of diabetic urine, but his experiments do not 

 prove that he actually met with this substance. Although I have 

 repeatedly sought for it, I have never been able to find xanthine in 

 diabetic urine ; indeed it has never been found in any specimen of 

 urine. 



Strahl and Lieberkiihnf believe that they have discovered 

 xanthine in human urine, but from the reactions which they describe, 

 the substance in question appears to have been guanine. 



[Dr. Dav) T t believes that the urinary secretion of scorpions and 

 spiders consists for the most part of xanthine. The substance he 

 has discovered is doubtless the same as that which Gorup-Besanez 

 and F. Will have regarded as guanine. See p. 173. G. E. D.] 



* Arch. d. Pharm. Bd. 11, S. 182. 



t Harnsaure im Blut u. s. w. Berlin, 1848, S. 112 ff. 



$ Ediii. New Phil. Jouru. Vol. 40, p. 338, and vol. 44, p. 125. 



