But, while keeping them separate, we can make these
fermentations follow each other, although, according to
the ideas of Liebig, they are interblended. Take this
liquid in which the lactic ferment has grown, and in
which there are only lactate of lime and mineral salts
in solution: after having heated it to sterilize it, sow
there a drop of a liquid in which there has occurred
spontaneously a butyric fermentation, and, therefore,
one which is almost surely impure. Phenomena anal-
ogous to those of alcoholic fermentation occur: a gas is
liberated which is no longer a pure carbonic acid, but a
mixture of this gas and hydrogen. This mixture has
very little odor, because of the absence of sulphuretted
hydrogen. These are the indications of a fermentation.
Let us see now what is present in the liquid which has
become clouded. We find there only motile rods, very
agile, with undulating movements, sometimes ranged in
a series, like a string of boats, and then motile on their
articulations ( Fig. 8, sec. 3 ), which testifies to the fact
that they reproduce and multiply by elongating and
segmenting across their longer axis; this is the mode of
reproduction called fission.

When he observed for the first time those organisms
which he called vibrios, Pasteur had a great surprise,
the trace of which is visible in his note on this subject.
The yeast of beer and the lactic ferment were non-motile
globules; the butyric ferment was motile, and partook
of the nature [animal] of those organisms which Ehren-
burg and Dujardin had found in infusions. O the power
of words! Nothing was more natural than to find in
fermentations the same organisms as in infusions, since
Pasteur nourished his ferments with vegetable infusions;
he hesitates, however, on finding that the butyric ferment
belongs to the Infusoria. "I was so far," he said, "from
expecting such a result, so far, indeed, that for a long

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