detail has a very great significance. The second process
is the only reasonably safe one.

On the contrary, the first method is liable frequently
to overlook the presence of the corpuscles, and we shall
see here how things go on in a research. The method
then adopted by Pasteur was the result of his false
idea. If Pasteur had considered these corpuscles as
parasites, he surely would have concluded that they
might be in one place and not in another, and that it
would be necessary to seek them in various places. But
he was convinced that the corpuscle, being a tardy sign
of the pre-existing disease, was a product of transforma-
tion, or, to employ a medical expression, a product of
retrogression of the cells of the tissues. Now, following
this hypothesis, it should occur everywhere in the body.

The method of research, imperfect because it had been
born of a false idea, deceived Pasteur and plunged him
deeper into his idea. In the eight couples brought
from Alais and which he had studied in Paris, he be-
lieved he had found one in which the male presented a
few corpuscles, and the female not any. As a matter of
fact, she also contained them, as shown by the result of
the cultures in which a few corpuscles appeared, not in
the worms and the chrysalids coming from these eggs
but in the moths. This phenomenon, spontaneous in
appearance, of corpuscles in a culture which it seemed
ought to be exempt, naturally confirmed Pasteur in his
belief in the internal origin of the corpuscle. It is thus
that a mode of examination inspired by a false idea leads
sometimes to the confirmation of this false idea, and it is
thus moreover that, during the whole of the campaign
of 1866, Pasteur persisted in likening the corpuscle to
pus-globules and even to red blood-globules. He came
back definitely to the idea of parasitism only after an
experiment of Gernez which we shall find in its place.

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