240 MR. E. SCHUNCK ON THE 



of various reagents. In the cases described by Janus Plancus,* 

 Prout,f Braconnot, J and Simon, || it existed in the former 

 state. Hassall developed the blue colour by means of putre- 

 faction, in urines exhibiting the usual appearance, while 

 Neubauer found the same effect to be produced by the ad- 

 dition of acids to the urine. As regards its chemical nature, 

 the blue colouring matter seems to have been of three kinds, 

 as far as can be ascertained from the descriptions given by the 

 observers, which are not always very precise. In some cases, 

 such as those described by Julia-Fontenelle, § and Cantu,^ 

 the colour was evidently caused by Prussian blue, the iron of 

 which appears to have been derived in one case from a quan- 

 tity of ink which the person had swallowed. The second 

 kind of colouring matter has been minutely described by 

 Braconnot, who obtained it simply by filtering the urine 

 from the blue deposit found suspended in it. It was a dark 

 blue powder, insoluble in water and alkalies, only slightly 

 soluble in alcohol and yielding no crystalline sublimate when 

 heated. From its dissolving in acids and its being reprecipi- 

 tated by alkalies and other bases, Braconnot inferred that it 

 consisted essentially of an organic base, to which he gave the 

 name of cyanourine. If the substance which he examined 

 was pure, it seems certainly to have been of a peculiar nature. 

 Nevertheless no one has since then observed any colouring 

 matter which could be with certainty pronounced identical 

 with it, though instances have been met with in which 

 the blue colour not being caused, as it seemed, by any well- 

 known body, has been attributed to the presence of cyanourine. 

 In the third class of cases the blue colour was produced by a 



* Commentarii Instituti Bononiensis, ad Ann. 1767. 



f On Stomach and Renal Diseases. 5th ed. p. &67. 



% Annales de Chimie et de Physique. T. XXIX. p. 252. 



|| Simon's Animal Chemistry, translated by Day. Vol. II. p. 327. 



§ Archives generates de Medecine. T. II. p. 104. 



% Journal de Chimie medicale. T. IX. p. 104. 



