inspired it was replaced by a true idea. For the cor-
puscle becoming, as it is really, the sole cause and not
simply the effect, or the witness, of the disease, its elimi-
nation was all the more profitable, and it is thus that
error sometimes leads to the truth. But let us not trust
too much to this example.

However this may be, Pasteur found himself led by
his manner of seeing things, to the same method of
egg-selection as Osimo, and it is curious to note with
what firmness, after 15 days only of sojourn in the places,
he indicates to the Agricultural Committee of Alais, ¹
the 26th of June, 1865, and repeats the 25th of September
following, before the Academy, the conditions of a good
method of egg-selection. "This means will consist in
isolating, at the moment of egg-laying, each couple,
male and female. After the mating, the female, set
apart, will lay her eggs; then one will open her, as well
as the male, in order to search therein for the corpuscles.
If they are absent both from male and female, he will
number this laying which shall be preserved as eggs
absolutely pure, and bred the following year with par-
ticular care. There will be eggs diseased in various
degrees according to the greater or less abundance of
the corpuscles in the male and female individuals which
have furnished them." ²

It is, on the whole, a return to the procedure of Osimo,
tried and judged worthless by Cantoni, as we have just
said. Why had it miscarried when it ought to have
succeeded? Perhaps because it had not been tried with
confidence, with the necessary faith, perhaps because
Cantoni had not sufficiently protected his worms from a
new contagion, the effects of which he had confounded
with those of heredity. When one follows an idea in

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