scientific man, these corpuscles existed normally in all
the moths.

A real progress had, however, been realized the day
that Osimo had discovered the corpuscles in the eggs
of silkworms, and the day Vittadini, after having rec-
ognized that their number increased in a laying of
eggs in proportion as they approached the period of
hatching, had based a method of distinguishing the
good from the bad upon a microscopic examination of the
eggs. The corpuscle is, indeed, actually, as we shall
see, the cause of the disease, and an egg which contains
it can never give cocoons; but these two facts not being
demonstrated, uncertainty existed as to the theoretic
value of the procedure. As to the practice, it often
gave out detestable eggs for good ones, and when it
condemned the eggs it was in the name of principles so
uncertain that the silk grower could not be held culpable
for having no confidence in the advice of science.

The same Osimo, in 1859, had endeavored to push
science and practice in another direction. He had ad-
vised examination not only of the eggs but also of the
chrysalids, and rejection of the layings of those stocks
which were found too corpuscular. This time it would
have been to approximate correct procedure, as we shall
see immediately, but this advice, given offhand, and
without experimental support, had been followed and
tested, offhand also, by Cantoni, who, after having
cultivated the eggs coming from non-corpuscular moths,
had seen the worms become corpuscular during the
culture, which proved, he had concluded, that "the
microscopic examination of moths was also unfortunately
as worthless" as the other remedies.

By good fortune, of all this past history, of all this
mixture of truth and falsehood, Pasteur knew nothing
at the beginning of his studies. To his complaint of

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