Putrid cabbage, green or boiled, infects the air in the very same manner
as putrid animal substances. Air thus tainted is equally contracted in
its dimensions, it equally extinguishes flame, and is equally noxious to
animals; but they affect the air very differently, if the heat that is
applied to them be considerable.

If beef or mutton, raw or boiled, be placed so near to the fire, that
the heat to which it is exposed shall equal, or rather exceed, that of
the blood, a considerable quantity of air will be generated in a day or
two, about 1/7th of which I have generally found to be absorbed by
water, while all the rest was inflammable; but air generated from
vegetables, in the same circumstances, will be almost all fixed air, and
no part of it inflammable. This I have repeated again and again, the
whole process being in quicksilver; so that neither common air nor
water, had any access to the substance on which the experiment was made;
and the generation of air, or effluvium of any kind, except what might
be absorbed by quicksilver, or resorbed by the substance itself, might
be distinctly noted.

A vegetable substance, after standing a day or two in these
circumstances, will yield nearly all the air that can be extracted from
it, in that degree of heat; whereas an animal substance will continue
to give more air, or effluvium, of some kind or other, with very little
alteration, for many weeks. It is remarkable, however, that though a
piece of beef or mutton, plunged in quicksilver, and kept in this degree
of heat, yield air, the bulk of which is inflammable, and contracts no
putrid smell (at least, in a day or two) a mouse treated in the same
manner, yields the proper putrid effluvium, as indeed the smell
sufficiently indicates.

That the putrid effluvium will mix with water seems to be evident from
the following experiment. If a mouse be put into a jar full of water,
standing with its mouth inverted in another vessel of water, a
considerable quantity of elastic matter (and which may, therefore, be
called _air_) will soon be generated, unless the weather be so cold as
to check all putrefaction. After a short time, the water contracts an
extremely fetid and offensive smell, which seems to indicate that the
putrid effluvium pervades the water, and affects the neighbouring air;
and since, after this, there is often no increase of the air, that seems
to be the very substance which is carried off through the water, as fa