tension, the different processes of vinegar-making by
oxidation of the alcohol in wine or fermented liquors.

Owing to his study of the different processes employed
in his vicinity, since the time of Schutzembach, by the
vinegar manufacturers of Germany, he had some right
to make this comparison. In a pile of casks with the
heads knocked in, and forming a hollow column several
meters in height, are piled loosely shavings of beech,
over which is showered a feebly alcoholic liquid to which
have been added some milligrams of acetic acid and which
contains, furthermore, a little acid beer, sharp wine, or
some other organic matter in process of alteration, neces-
sary, according to the theory of Liebig, to act as a fer-
ment and set in motion the phenomenon. Under these
conditions the shavings play the rôle of the platinum
black and do it more economically. On coming into
contact with them the alcohol oxidizes, the mass be-
comes heated, and the pile of casks forms achimney for
a current of air, which, entering below, diffuses through-
out the mass, bringing constantly to all points new oxy-
gen, so that the process of acetification progresses
rapidly. As with platinum black, there are sometimes
formed, in addition to the acetic acid, suffocating prod-
ucts with the odor of aldehyde. Finally, to complete
the resemblance, the shavings seem to act only by their
presence. After 10 or 20 years of use in the manufacture
of vinegar, they are intact, being as sound and clean as
on the first day.

We will acknowledge that the comparison was tempt-
ing, and will understand that Liebig could not resist the
temptation. One falls easily on the side toward which
he leans. Pasteur was entitled to look upon the question
quite differently. In connection with his studies on
spontaneous generation, he had just determined that all
organic substances oxidize very slowly in contact with

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