7l6 PHILOSOPHICAL TRANSACTIONS. [anNO 1790. 



animal substances recently boiled. Hence it appears, that the matter on which 

 the peculiar smell of cancerous ulcers depends, is a very volatile substance, for it 

 escaped at the beginning of the process. It also appears that this volatile sub- 

 stance, which is probably the active principle in the matter of cancer, is not 

 changed, by simple exposure to heat, into a permanently elastic fluid ; for the 

 air that escaped at the beginning of the process, though it smelled strongly of the 

 cancerous matter, was found by Dr. Priestley's test to be as pure as common air; 

 and it was evident, that the aqueous vapour which came over in the middle of the 

 process was not mixed with any permanently elastic fluid ; because, when this 

 vapour was received in an inverted bottle filled with mercury, it was condensed 

 into water, without any admixture of air. Indeed, if the odoriferous principle in 

 the matter of cancer consist of volatile alkali combined with animal hepatic air, 

 it could not be expected that it should acquire a permanently elastic form by sim- 

 ple exposure to heat ; because when alkaline and animal hepatic air unite toge- 

 ther, they form a non-elastic substance that condenses on the inner surface of the 

 vessel in which they are mixed. 



To discover whether other animal substances yield an aerial fluid, similar to 

 that which was extricated in the foregoing experiment from the matter of cancer 

 by means of heat, a portion of the flesh of the neck of a chicken was introduced 

 into a small coated glass retort, which was gradually exposed to heat in a sand 

 bath till it became red-hot. A thin phlegm, of a yellowish colour, first came 

 over : this was soon succeeded by a yellow empyreumatic oil, and at the same 

 time a permanently elastic fluid, having an odour resembling that of burnt fea- 

 thers, began to be disengaged. A slip of paper, tinged with litmus and reddened 

 by acetous acid, being held over this fluid, became blue. The neck of the retort 

 was now introduced below an inverted jar filled with mercury, and a considerable 

 quantity of air, together with a fetid empyreumatic oil, were received in the jar. 

 This air was highly inflammable : it had a very fetid odour. When a bottle', 

 containing a portion of it, was agitated with distilled water, nearly one-half of it 

 was absorbed. The residue was inflammable, and burned first with a slight ex- 

 plosion, and afterwards with a blue lambent flame. A little nitrated silver being 

 dropped into the water with which the air had been agitated, the mixture in- 

 stantly acquired a reddish brown colour; after some time it became turbid, and a 

 brown precipitate fell to the bottom. When 2 measures of the air, extricated in 

 this experiment, were mixed with 1 of alkaline air, they occupied the space of a 

 little more than 1 measure and a half. A 2d measure of alkaline air being added, 

 and the airs being suffered to remain together for 3 days, at the end of that time 

 the residue occupied the space of 2-^ measures. Soon after they were mixed, an 

 oily fluid, of a pale colour, was deposited on the internal surface of the jar. At 

 the end of the 3d day this substance had acquired a light olive colour. It was 



