in Section XXXIII. 3. 2. Oxygen in combination with
metals, when applied in certain quantity, produces this effect by its
stimulus; and the metallic oxydes not being decomposed by their contact
with animal matter, no new acid, or contagious material, is produced. So
that the combined oxygen, when applied to an ulcer, simply I suppose
promotes absorption in it, like the application of other materials of the
articles sorbentia or incitantia, if applied externally; as opium, bark,
alum. But in the pulmonary ulcers, which cannot protect themselves from the
air by forming a scab, the uncombined oxygen of the atmosphere unites with
the purulent matter, converting it into a contagious ichor; which by
infection, not by erosion, enlarges the ulcers, as in the itch or tinea;
which might hence, according to Dr. Beddoes's ingenious theory of
consumption, be induced to heal, if exposed to an atmosphere deprived of a
part of its oxygen. This I hope future experiments will confirm, and that
the pneumatic medicine will alleviate the evils of mankind in many other,
as well as in this most fatal malady.

M. M. First, the respiration of air lowered by an additional quantity of
azote, or mixed with some proportion of hydrogen, or of carbonic acid air,
may be tried; as described in a late publication of Dr. Beddoes on the
medicinal use of factitious airs. Johnson, London. Or lastly, by breathing
a mixture of one tenth part of hydro-carbonate mixed with common air,
according to the discovery of Mr. Watt, which has a double advantage in
these cases, of diluting the oxygen of the atmospheric air, and inducing
sickness, which increases pulmonary absorption, as mentioned below. An
atmosphere diluted with fixed air (carbonic acid) might be readily procured
by setting tubs of new wort, or fermenting beer, in the parlour and
lodging-room of the patient. For it is not acids floating in the air, but
the oxygen or acidifying principle, which injures or enlarges pulmonary
ulcers by combining with the purulent matter.

Another easy method of adding carbonic acid gas to the air of a room, would
be by means of an apparatus invented by Mr. Watt, and sold by Bolton and
Watt at Birmingham, as described in Dr. Beddoes' Treatise on Pneumatic
Medicine. Johnson, London. It consists of an iron pot, with an arm
projecting, and a method of letting water drop by slow degrees on chalk,
which is to be put into the iron pot, and exposed to a moderate degree of
heat ove