tion, that is to say one of the maladies to which wine is
constantly exposed, is exclusively the work of a micro-
organism. But there are many other diseases which
invade wines with more or less rapidity. The wines of
Bordeaux turn, those of Burgundy become bitter, the
wines of Champaigne become ropy. At this time, the
Phylloxera had not yet made its appearance, and many
persons had caves; but there was no cave where a malady
of the wine did not appear from time to time, and did
not cause losses, which were often grievous.

Upon that point, the ideas of Liebig shed no great light.
According to them, the wine was constantly in move-
ment, at work; those wines which preserved themselves
intact, and were called de garde, reached the end of
fermentation with a certain state of equilibrium between
their sugar and their organic matter serving as ferment;
these two elements were equally exhausted. If there
had been too little ferment in the beginning, a portion of
the sugar remained unchanged, and the wine was sweet,
that is to say incomplete. If there had been too little
sugar, on the contrary, some ferment remained which
continued to work upon the substance and to produce
therein vitiations of the taste. This explanation, so
beautifully symmetrical, had seduced people's minds,
and the reader found it paraphrased in all the books on
the subject. As to a remedy, it did not give any, or at
least it had not done so.

For Pasteur, on the contrary, these ideas had no mean-
ing. He was sure that the activity of the yeast was
arrested after having transformed the sugar, and that
it could act neither upon the alcohol which it had
formed, nor upon the other elements of the wine. In
that he was deceived, for we have seen since that the
yeast can destroy in time the glycerin which it has
produced, just as the mycoderma of the vinegar burns the

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