rto in ignorance whether plants or germs of
any kind have had anything to do with his operations. Still, when the
fermented grape-juice is examined, the living Torula concerned in
alcoholic fermentation never fails to make its appearance. How is
this? If no living germ has been introduced into the wine-vat, whence
comes the life so invariably developed there?

You may be disposed to reply, with Turpin and others, that in virtue
of its own inherent powers, the grape-juice when brought into contact
with the vivifying atmospheric oxygen, runs spontaneously and of its
own accord into these low forms of life. I have not the slightest
objection to this explanation, provided proper evidence can be adduced
in support of it. But the evidence adduced in its favour, as far as I
am acquainted with it, snaps asunder under the strain of scientific
criticism. It is, as far as I can see, the evidence of men, who
however keen and clever as observers, are not rigidly trained
experimenters. These alone are aware of the precautions necessary in
investigations of this delicate kind. In reference, then, to the life
of the wine-vat, what is the decision of experiment when carried out
by competent men? Let a quantity of the clear, filtered 'must' of the
grape be so boiled as to destroy such germs as it may have contracted
from the air or otherwise. In contact with germless air the
uncontaminated must never ferments. All the materials for spontaneous
generation are there, but so long as there is no seed sown, there is
no life developed, and no sign of that fermentation which is the
concomitant of life. Nor need you resort to a boiled liquid. The
grape is sealed by its own skin against contamination from without. By
an ingenious device Pasteur has extracted from the interior of the
grape its pure juice, and proved that in contact with pure air it
never acquires the power to ferment itself, nor to produce
fermentation in other liquids. [Footnote: The liquids of the healthy
animal body are also sealed from external contamination. Pure blood,
for example, drawn with due precautions from the veins, will never
ferment or putrefy in contact with pure air.] It is not, therefore,
in the interior of the grape that the origin of the life observed in
the vat is to be sought.

What then is its true origin? This is Pasteur's answer, which his
well-proved accuracy renders worthy of all confidence. At the time of
the vintage microscopic part