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DUST AND DISEASE. 309

Iution of caustic potash, the other sulphuric acid. “ All the
bent tubes,” says Dr. Bennett, “ were filled with fragments
of pumice-stone to break up the air, so as to prevent the
possibility of any germs passing through in the centre of
bubbles.” The air also passed through a Liebig’s bulb
containing sulphuric acid, and also through a bulb contain-
ing gun-cotton.

It was only natural for Dr. Bennett to believe that his
bent tubes entirely cut off the germs. Previous to the
observations just referred to I also believed in their compe-
tence to do this. But these observations destroy any such
notion. The gun-cotton, moreover, will fail to arrest the
Whole of the floating matter unless it is tightly packed,
and there is no indication in Dr. Bennett’s memoir that it
was so packed. On the whole, I should infer from the
mere inspection of the apparatus the very results which
Dr. Bennett has described—a retardation of the develop-
ment of life, a total absence of it in some cases, and its
presence in others.

In his first series of experiments eight flasks were fed
with his sifted air, and five with common air. In ten or
twelve days all the five had fungi in them; while it re-
quired from four to nine months to develop fungi in the
others. In one case, moreover, even after this interval, no
fungi appeared. In a second series of experiments there
was a similar exception. In a third series of experiments
he abandoned the cork stoppers used in the first and second
series, and employed glass stOppers. Flasks containing
decoctions of tea, beef, and hay, were filled with common
air, and other flasks with sifted air. In every one of the
former fungi appeared, and in not one of the latter. These
experiments simply ruin the doctrine that Dr. Bennett
finally esPouses.

In all these oases the prepared air was forced into the
infusion when it was boiling hot. Dr. Bennett made a

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