Dr. Schunck on the Occurrence of Indigo-blue in Urine. 289 
These urines have been observed in diseases of the most different 
kinds, as well as in cases in which the general health seemed not 
to be in the least degree affected. The pigments themselves,:to 
which the colours are due, have not until lately been subjected 
to any chemical examination, and great doubts still prevail 
regarding their true nature. The blue pigment to which I pro- 
pose to confine myself on the present occasion, has been dis- 
covered in two states. In some cases it has been found ready 
formed so as to impart to the urine a blue colour, but merely in 
a state of suspension and therefore easily separated by simple 
filtration, whereas in other cases it has only made its appearance 
when the urine was left to stand or was subjected to the action 
of various reagents. In the cases described by Janus Plancus*, 
Proutt, Braconnott, and Simon §, it existed in the former state. 
Hassall developed the blue colour by means of putrefaction, in 
urines exhibiting the usual appearance, while Neubauer found 
the same effect to be produced by the addition 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 quantity of ink which the person had swal- 
lowed. The second kind of colouring matter has been minutely 
described by Braconnot, who cbtained 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 reprecipitated 
by alkalies and other bases, Braconnot inferred that it consisted 
essentially of an organic base, to which he gave the name of 
eyanourine. 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 cyanourme. In the third class of cases the 
blue colour was produced by a substance, which, on examination 
*« Commentarii Instituti Bononiensis, ad ann. 1767. 
+ On Stomach and Renal Diseases. 5th ed. p: 567. 
} Annales de Chimie et de Physique, vol. xxix. p. 252. 
§ Simon’s Animal Chemistry, translated by Day, vol ii. p. 327. 
|| Archives générales de Médecine, vol. ii. p. 104. 
§{ Journal de Chimie médicale, vol. ix. p. 104. 
Phil, Mag, 8, 4, Vol, 14, No. 98, Oct, 1857, U 
