OF INDIGO IN HUMAN URINE. 
303 
like deposit, which was more than an inch in depth in a six-ounce bottle. Examined 
with the microscope, no crystalline deposit of any kind was discovered ; the bottle 
was kept corked until May 21, the urine undergoing - no particular change during 
the interval, but only getting a little deeper-coloured. On that date it was poured 
into a glass ; by the 24th the urine had changed colour greatly, and a good deal of 
blue, visible to the naked eye, had formed upon the surface. On the following day 
the surface had become deep indigo-blue all over, and the urine was thick and of a 
dull grass-green colour ; some of the blue colouring matter had become deposited 
upon the layer of mucus at the bottom of the glass, but there was no sediment of 
brown extractive. On the 26th the fluid had become more bluish-green, and was 
very deep-coloured ; it also contained triple phosphate, Vibriones, and the usual 
animalcules. By the 28th much of the blue matter had fallen as a deposit, and the 
liquid had become brownish-green ; a day or two later it was tawny brown ; the blue 
colouring matter which had not subsided as a deposit, adhered to the sides of the 
glass, forming a broad, deep blue ring round its circumference. This urine was 
chiefly remarkable for the extraordinary rapidity with which it changed colour, and 
with which the blue colouring matter was developed. The changes were so rapid, 
that every hour was observed to make a considerable difference in the appearance 
and characters of the urine. This is possibly explained by the supposition, that while 
in the corked bottle, the substance afterwards developed into blue indigo had 
undergone a certain amount of change through the limited access of oxygen. 
Chemical analysis proved that in this case likewise the colouring matter possessed 
the usual characters of indigo ; it gave a blue solution with sulphuric acid, was 
decolorized by chlorine and nitric acid, and it sublimed in violet-red vapours when 
heated in a test-tube # . 
I have now to observe that I have detected the presence of indigo in human 
urine in a variety of other cases besides the above, of all which 1 have preserved 
memoranda. In some the quantity of indigo was, as in the three examples above 
referred to, very considerable ; the urine in some of them was coloured with it, or a 
deep blue pellicle formed on the surface. In many of the remaining cases, on the 
other hand, the quantity was less considerable; the scutn on the surface was only 
slightly coloured, or the quantity was so small as to require the microscope for its 
detection. In nearly all of these instances the blue colouring matter was subjected 
to analysis ; where the amount was so small that it could only be detected by the 
microscope, it was tested by reagents, such as sulphuric acid, liquor potassae, &c., 
applied while the blue fragments were under the object-glass of the microscope. 
Where the urine was high-coloured and acid, and where the quantity of the blue 
colouring matter was but small, I have observed it to be deposited in the threads of 
the thallus of the fungus Penicilium glaucum, forming patches which to the eye 
* A portion of the blue pigment formed in this case accompanied my previous communication to the Royal 
Society. 
