icles are observed adherent, both to the
outer surface of the grape and of the twigs which support the grape.
Brush these particles into a capsule of pure water. It is rendered
turbid by the dust. Examined by a microscope, some of these minute
particles are seen to present the appearance of organised--cells.
Instead of receiving them in water, let them be brushed into the pure
inert juice of the grape. Forty-eight hours after this is done, our
familiar Torula is observed budding and sprouting, the growth of the
plant being accompanied by all the other signs of active fermentation.
What is the inference to be drawn from this experiment? Obviously
that the particles adherent to the external surface of the grape
include the germs of that life which, after they have been sown in the
juice, appears in such profusion. Wine is sometimes objected to on
the ground that fermentation is 'artificial;' but we notice here the
responsibility of nature. The ferment of the grape clings like a
parasite to the surface of the grape; and the art of the wine-maker
from time immemorial has consisted in bringing--and it may be added,
ignorantly bringing--two things thus closely associated by nature into
actual contact with each other. For thousands of years, what has been
done consciously by the brewer, has been done unconsciously by the
wine-grower. The one has sown his leaven just as much as the other.

Nor is it necessary to impregnate the beer-wort with yeast to provoke
fermentation. Abandoned to the contact of our common air, it sooner
or later ferments; but the chances are that the produce of that
fermentation, instead of being agreeable, would be disgusting to the
taste. By a rare accident we might get the true alcoholic
fermentation, but the odds against obtaining it would be enormous.
Pure air acting upon a lifeless liquid will never provoke
fermentation; but our ordinary air is the vehicle of numberless germs
which act as ferments when they fall into appropriate infusions. Some
of them produce acidity, some putrefaction. The germs of our
yeast-plant are also in the air; but so sparingly distributed that an
infusion like beer-wort, exposed to the air, is almost sure to be
taken possession of by foreign organisms. In fact, the maladies of
beer are wholly due to the admixture of these objectionable ferments,
whose forms and modes of nutrition differ materially from those of the
true leaven.

Working in an atmosphere charge