master more and more anxious. He kept us so remote
from his thought that we could not explain his uneasiness
till that day when he appeared before us almost in tears,
and, dropping discouraged into a chair said: "Nothing
is accomplished; there are two diseases!"

He had in mind this disease of the morts-flats, con-
cerning which I have already made brief mention.
He had known it for a long time, indeed since his
first sojourn in the South in 1865, where one of the two
cultures of silkworms which served for the beginning
of his deductions was attacked by this disease at the
same time as by that of the corpuscles. But the cases
of association were so frequent, precisely because the
disease of the corpuscles was widespread, that Pasteur
had considered the two affections as intimately con-
nected and likely to disappear together.

During the silkworm cultures of 1866, the two diseases
were somewhat separated both in fact and in his mind.
He had sometimes seen the second appear in cultures
hereditarily exempt from the first, and he had asked
himself whether they were not independent. His pub-
lications at this time bear the trace of these preoccupa-
tions, which had not yet become a source of uneasiness.
The cases of morts-flats had been rare, and had besides
appeared here and there, without visible preference,
like cultural accidents attributable to the growers.

It was in 1867, in the preliminary trials, and especially
In the large cultures, that the gravity of the danger first
appeared. Almost entire lots of eggs free from cor-
puscles and bred by various growers had perished
everywhere of the disease known as morts-flats, what-
ever might be the circumstances of place, time, climate
and culture. It could not be any longer a question of
accidents: it was the manifestation of an inherited dis-
position, and on seeing these mishaps renewed, on finding

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