of Cancer, and on Animal Hepatic Air* 393 
the addition of the acid, the liquor, as before, acquired a brown 
colour, its fetor was much increafed, and a manifeft effervef- 
cence took place, although it was not fo confiderable as in the 
former inftance. A portion of the fame matter diffufed through 
diftilled water communicated a blue tinge to tindture of litmus, 
and a greenifti caft to fyrup of violets. 
It is proper to obferve, that when fyrup of violets was mixed 
with portions of cancerous matter from a variety of different 
fubjedts, the change produced was in fome cafes fcarcely per- 
ceptible ; but in every inftance the prefence of an alkali was 
detedled by dipping into the matter a flip of paper that had 
been previoufly tinged blue by tindlure of litmus, and after* 
wards flightly reddened by acetous acid. The red colour was 
invariably in the courfe of a few minutes abolifhed, and the 
blue reftored. 
The cancerous matter, as has been already remarked, ac* 
quired, upon the addition of the vitriolic acid, a brown hue. 
It is well known, that this acid, when it is highly concen* 
trated, communicates a brown or black colour to all animal and 
vegetable fubftances. Being deiirous of learning whether th& 
change which took place upon the addition of the acid to the 
cancerous matter in this experiment, was different from that 
which would be produced by the fame acid in other animal 
fubftances, and particularly in recent healthy pus ; I took 
equal quantities of the latter, and of afh- coloured cancerous 
matter, and having diffufed each of them through thrice its 
weight of diftilled water, I added to them equal quantities of 
concentrated vitriolic acid; the weight of the acid being nearly 
the fame with that of the matter ufed in the experiment. The 
mixture containing the pus acquired from the acid a faint brown 
colour; but that which contained the cancerous matter, was 
Vol. LXXX. F f f fuddenly 
