ct-glass of the microscope should come very close to the
organisms. Round the edge of the circular plate of glass the liquid
is in contact with the air, and incessantly absorbs it, including the
oxygen. Here, if the drop be charged with bacteria, we have a zone of
very lively ones. But through this living zone, greedy of oxygen and
appropriating it, the vivifying gas cannot penetrate to the centre of
the film. In the middle, therefore, the bacteria die, while their
peripheral colleagues continue active. If a bubble of air chance to
be enclosed in the film, round it the bacteria will pirouette and
wabble until its oxygen has been absorbed, after which all their
motions cease. Precisely the reverse of all this occurs with the
vibrios of butyric acid. In their case it is the peripheral organisms
that are first killed, the central ones remaining vigorous while
ringed by a zone of dead. Pasteur, moreover, filled two vessels with
a liquid containing these vibrios; through one vessel be led air, and
killed its vibrios in half an hour; through the other he led carbonic
acid, and after three hours found the vibrios fully active. It was
while observing these differences of deportment fifteen years ago that
the thought of life without air, and its bearing upon the theory of
fermentation, flashed upon the mind of this admirable investigator.

*****

We now approach an aspect of this question which concerns us still
more closely, and will be best illustrated by an actual fact. A few
years ago I was bathing in an Alpine stream, and returning to my
clothes from the cascade which had been my shower-bath, I slipped upon
a block of granite, the sharp crystals of which stamped themselves
into my naked shin. The wound was an awkward one, but being in
vigorous health at the time, I hoped for a speedy recovery. Dipping a
clean pocket-handkerchief into the stream, I wrapped it round the
wound, limped home, and remained for four or five days quietly in bed.
There was no pain, and at the end of this time I thought myself quite
fit to quit my room. The wound, when uncovered, was found perfectly
clean, uninflamed, and entirely free from matter. Placing over it a
bit of goldbeater's-skin, I walked about all day. Towards evening
itching and heat were felt; a large accumulation of matter followed,
and I was forced to go to bed again. The water-bandage was restored,
but it was powerless to check the action now set up; arnica was
app