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of infection. He inoculated healthy worms with the cor-
pusculous matter, and watched the consequent growth of
the disease. He showed how the worms inoculate each
other by the infliction of visible wounds with their claws.
In various cases he washed the claws, and found corpuscles
in the water. He demonstrated the spread of infection by
the simple association of healthy and diseaSed worms. The
diseased worms sullied the leaves by their dejections, they
also used their claws, and spread infection in both ways.
It was no hypothetical infected medium that killed the
worms, but a definitely-organized and isolated thing. He
examined the question of contagion at a distance, and de-
monstrated its existence. In fact, as might be expected
from Pasteur’s antecedents, the investigation was exhaus-
tive, the skill and beauty of his manipulation finding fitting
correlatives in the strength and clearness of his thought.

The following quotation from Pasteur’s work clearly
shows the relation in which his researches stand to this
great question:

“Place,” he says, “ the most skilful educator, even the most expert
micrOSCOpist, in presence of large educations which present the symp-
toms described in our experiments; his judgment will necessarily be er-
roneous if he confines himself to the knowledge which preceded my re-
searches. The worms will not present to him the slightest spot of
pébrine ; the microscOpe will not reveal the existence of corpuscles ; the
mortality of the worms will be null or insignificant; and the cocoons
leave nothing to be desired. Our observer would, therefore, conclude
without hesitation that the eggs produced will be good for incubation.
The truth is, on the contrary, that all the worms of these fine crops have
been poisoned ; that, from the beginning, they carriedin them the germ
of the malady; ready to multiply itself. beyond measure in the Chrysa-
lides and the moths, thence to pass into the eggs and smite with sterility
the next generation. And what is the first cause of the evil concealed
under so deceitful an exterior ? In our experiments we can, so to speak,
touch it with our fingers. It is entirely the effect of a single corpuscu-
lous repast; an effect more or less prompt according to the epoch of life
of the worm that has eaten the poisoned food.”

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