OCCURRENCE OF INDIGO-BLUE IN URINE. 241 



substance, which on examination of its properties and reac- 

 tions was found to be indigo-blue. Prout and Simon each 

 I ion a case in which indigo-blue was deposited from urine 

 on standing, in the shape of a blue sediment. Neubauer* 

 observed that the urine of a young man of 18, apparently in good 

 health, when mixed with strong acids became first purple, then 

 , and deposited a blue powder, which however he could 

 not with positive certainty identify as indigo-blue. Hassall t 

 was the first to point out that the occurrence of indigo-blue 

 in urine was by no means so rare a phenomenon as had 

 previously been supposed. The specimens of urine in which 

 1 [assail discovered it were mostly of a pale straw colour and 

 acid. On standing they became thick and turbid and changed 

 in colour from yellow to brown then to bluish-green, while 

 the surface became covered with a blue scum or pellicle, which 

 was found to consist of impure indigo-blue. Hassall con- 

 rid< n that the exposure of the urine to the oxygen of the 

 atmosphere is essential for the formation of the colouring 

 matter, however I shall show that this exposure is by no 

 means necessary. He also maintains that indigo-blue does 

 not occur in healthy urine, that its presence is accompanied 

 with strongly-marked symptoms of deranged health, and that 

 •rmation in urine must be regarded as a strictly patho- 

 logical phenomenon, conclusions which are, as will be seen, 

 quite at variance with the results of my experiments. 



Such in a few words is the present state of our knowledge 

 on this rather obscure subject. 



In my paper " On the Formation of Indigo-blue," J I have 

 shown that the colouring matter exists in plants in a very 

 different state to what had hitherto been supposed, that it does 



* Anleitung zur Analyse des Harris. S. IP. 



f Proceedings of the Royal Society, Vol. VI. p. 827 ; and Philosophical 

 Transactions for 1*54, p. 297. 

 X Memoirs of the Literary and Philosophical Society of Manchester, Vol. 

 p. 177 ; and M On the Formation of Indigo-blue," in the present Vol. 

 2 I 



