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DUST AND DISEASE. 289

from sugar to sulphate of quinine—all has been invoked in
behalf of this unhappy insect.” The helpless cultivators,
moreover, welcomed with ready trustfulness every new
remedy, if only pressed upon them with sufficient hardi-
hood. It seemed impossible to diminish their blind confi-
dence in their blind guides. In 1863 the French Minister
of Agriculture himself signed an agreement to pay 500,000
francs for the use of a remedy which its promoter declared
to be infallible. It was tried in twelve different depart-
ments of France, and found perfectly useless. In no single
instance Was it successful. It was under these circum-
stances that M. Pasteur, yielding to the entreaties of his
friend, betook himself to Alais in the beginning of June,
1865. As regards silk husbandry, this was the most im-
portant department in France, and it was also that which
had been most sorely smitten by the epidemic.

The silk-worm had been previously attacked by mus-
cardz'ne, a disease proved by Bassi to be caused by a vege-
table parasite. Though not hereditary, this malady was
propagated annually by the parasitic spores, which, wafted
by winds, often sowed the disease in places far removed
from the centre of infection. Muscardine is now said to
be very rare; but for the last fifteen or twenty years a
deadlier malady has taken its place. A frequent outward
sign of this new disease are the black spot-s which cover
the silk-worms, hence the name pébm‘ne, first applied to
the plague by M. de Quatrefages, and adOpted by Pasteur.
Pébrine declares itself in the stunted and unequal growth
of the worms, in the languor of their movements, in their
fastidiousness as regards food, and in their premature
death. The track of discovery as regards the epidemic
is this: In 1849 Guerin Méneville noticed in the blood
of silk-worms vibratory corpuscles which he supposed to
be endowed with independent life. Filippi proved him
wrong, and showed that the motion of the corpuscles was

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