After Pasteur, Cohn had studied the mode of formation
and the resistance of these spores in Bacillus subtilis, and
had put forth the hypothesis that the bacteria of an-
thrax possibly behaved like this bacillus. But none
of these precedents detract in the least from the merit
of Koch: it was he who showed the rôle of the spore in
the etiology of anthrax, and he did it in a way truly mar-
vellous for its simplicity.

If one places in the thermostat or even leaves exposed
to summer heat a drop of fresh beef-blood serum or of
the aqueous humor of the eye, sown with a very small
fragment of fresh spleen from a mouse affected with
anthrax, a microscopical examination at the end of
15 to 18 hours shows the following appearances: in the
center of the slide which covers the preparation, where
the air cannot penetrate easily, the bacilli are in their
original state and have not elongated. Half way, from
the edges of the cover-glass the bacilli are longer, twisted
and bent and so much the more elongated as they are
nearer the margin. Certain ones, those which are most
in contact with the outer air, contain typical spores,
sometimes arranged regularly in the filament like beads
( Fig. 20, left side). Ultimately these free themselves
from the envelope in which they are formed. They
are then disseminated through the liquid like an amor-
phous powder. But this dust is living, for, if transferred
to a new drop of serum, there spores produce at the end
of 3 or 4 hours new bacilli, capable, like the first, of
causing the death of the animal inoculated with them.
There is then no diminution of virulence in passing
through the spore state.

We see that Koch, passing over and beyond Davaine,
who had not thought of it, was not satisfied to repeat
Delafond's cultural experiments. He succeeded in the
first attempt in doing that which Delafond had tried

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