irreproachable and always successful, but no such were
available. Experiments which had been the most con-
vincing often failed, without any one being able to tell
why. Even to-day, when our technic is better, we can
not be sure of obtaining the results of Spallanzani.
Tyndall, whose experimental skill was very great, has
often repeated in vain the experiments of Schultze. In
short, there were certain substances, milk, albumen,
macerations of meat, which neither filtration, nor heating
of the air preserved from alteration, and we have seen
that Helmholtz admitted for these substances a kind of
spontaneous generation. But to admit it in one case,
was to admit it in all. Wherever there was a doubtful
case, one flask remaining fertile in spite of the precau-
tions taken, spontaneous generation had the right to
seize upon this result, and to say "It is I who have pro-
duced this. Life is a fragile thing to preserve; more
fragile still to produce. It is all to no purpose that you
train your fingers to manipulate it delicately; you thwart
it without knowing it, and it is sometimes just because
you are unskilful that you see it appear."

And these were not the only reasons. The partisans
of spontaneous generation had the best of it in the dis-
cussion, and they could say: "We who do not know on
what life depends and who make it arise from nothing,
we are exempt from the obligation of showing you its
origin and causes. But you who attribute it to pre-
existing germs, show us then these germs! Above all,
show them to us in sufficient number and variety so
that each bubble of air can people with numerous and
varied organisms the various infusions which we may
ask it to fecundate. For, finally, specificity is one of the
consequences of your way of looking at things. But we
have not forgotten a certain experiment of Gay-Lussac
in which some grape juice, sterile at first, was made to

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