of
infusorial life.

Here again the success of Schulze was due to his working in
comparatively pure air, but even in such air his experiment is a very
risky one. Germs will pass unwetted and unscathed through sulphuric
acid unless the most special care is taken to detain them. I have
repeatedly failed, by repeating Schulze's experiments, to obtain his
results. Others have failed likewise. The air passes in bubbles
through the bulbs, and to render the method secure, the passage of the
air must be so slow as to cause the whole of its floating matter, even
to the very core of each bubble, to touch the surrounding liquid. But
if this precaution be observed, water will be found quite as effectual
as sulphuric acid. By the aid of an air-pump, in a highly infective
atmosphere I have thus drawn air for weeks without intermission, first
through bulbs containing water, and afterwards through vessels containing
organic infusions, without any appearance of life. The germs were not
killed by the water, but they were effectually intercepted, while the
objection that the air had been injured by being brought into contact
with strongly corrosive substances was avoided.

The brief paper of Schulze, published in Poggendorf's Annalen for
1836, was followed in 1837 by another short and pregnant communication
by Schwann.

Redi, as we have seen, traced the maggots of putrefying flesh to the
eggs of flies. But he did not and he could not know the meaning of
putrefaction itself. He had not the instrumental means to inform him
that it also is a phenomenon attendant on the development of life.
This was first proved in the paper now alluded to. Schwann placed
flesh in a flask filled to one-third of its capacity with water,
sterilised the flask by boiling, and then supplied it for months with
calcined air. Throughout this time there appeared no mould, no
infusoria, no putrefaction; the flesh remained unaltered, while the
liquid continued as clear as it was immediately after boiling. Schwann
then varied his experimental argument, with no alteration in the
result. His final conclusion was, that putrefaction is due to
decompositions of organic matter attendant on the multiplication
therein of minute organisms. These organisms were derived not from
the air, but from something contained in the air, which was destroyed
by a sufficiently high temperature. There never was a more determined
opponent of the doctrine of spontaneous generat