290 Dr. Schunck on the Occurrence of Indigo-blue in Urine. 
of its properties and-reactions, was found to be indigo-blue. 
Prout and Simon each mention a case in which indigo-blue was 
deposited from urine on standing, in the shape of a blue sedi- 
ment. Neubauer* observed that the urine of a young man of 
18, apparently in good health, when mixed with strong acids be- 
came first purple, then blue, and deposited a blue powder, which 
however he could not with positive certainty identify as indigo- 
blue. Hassall} was the first to point out that the oceurrence of 
indigo-blue in urine was by no means so rare a phenomenon as 
had previously been supposed. The specimens of urine in which 
Hassall 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 consistof impure indigo-blue. Hassall considers 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 its formation in urine must be regarded as 
a strictly pathological phenomenon,—conclusions which are, 
as will be seen, quite at variance with the results of my ex- 
periments. 
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-bluet,”’ I have 
shown that the colouring matter exists in plants in a very differ- 
ent state to what had hitherto been supposed, that it does not 
exist in them ready formed nor as reduced indigo, and that the 
presence of oxygen is not essential to its formation, but that it 
owes its origin to the presence of a peculiar substance, soluble in 
water, alcohol and ether, which by the action of acids is decom- 
posed into indigo-blue, to which I have given the name of 
Indican, also a peculiar kind of sugar and a small quantity of 
other products. After having investigated the properties of this 
substance and its products of decomposition, I conceived it to be 
a matter of great interest to ascertain in what state indigo-blue 
exists in those urines, in which its presence is not indicated by 
the external appearance, but is only made manifest by treatment 
with various reagents. That such urines should contain a body 
* Anleitung zur Analyse des Harns, p. 19. 
t Philosophical Magazine for September 1853; and Philosophical 
Transactions for 1854, p. 297. 
{ Phil. Mag. vol. x. [4] p. 73. 
ii 
