of Cancer , and on Animal Hepatic Air . 595 
which foon afterwards acquired a brownifh purple hue, and at the 
end of two hours the colour of the mixture was changed to a deep 
brown. The fetid fmell was now rendered much fainter than 
that of a fimilar mixture of cancerous matter, and of diftilled 
water, to which nitrated filver had not been added. When a 
little concentrated nitrous acid was dropped into the mixture 
which had been thus altered by the addition of nitrated filver, 
a flight effervefcence took place, the brown hue was inftantiy 
changed to an orange colour, and the fetid fmell was abolifhed* 
The fetor was likewife entirely deftroyed, when dephlogifti- 
cated marine acid was added either to cancerous matter in its 
feparate ftate, or to a portion of that fubftance which had been 
previoufly mixed with nitrated filver. 
By the foregoing properties the cancerous virus is diftinguifhed 
from common pus : for when dilute vitriolic acid is added to com* 
mon pus, no effervefcence is produced ; and when a foluticn of 
nitrated filver is dropped into this fubftance previoufly diffufed 
through diftilled water, the mixture does not acquire a brown co- 
lour ; nor does any fenfible precipitation take place for feveral 
hours. It appeared, however, that when the laft experiment was 
repeated with matter obtained from a venereal bubo, the mixture 
upon the addition of the nitrated filver became flightly turbid, 
and, at the end of two hours, it acquired a brownifh caft. The 
fame effects were perceived when the trial was made with mat- 
ter obtained from a carious bone. But in thefe in fiances the 
precipitation was much lefs confiderable than that which was 
produced by the cancerous matter. 
I next endeavoured to procure, in its feparate ftate, a por- 
tion of the air which is extricated from the matter of cancer 
by the vitriolic acid. With this intention a quantity of red- 
difh cancerous matter was mixed in a fmall proof, with about 
F f f 2 ? thrice 
