became cent. per cent. The number
of corpuscles would at the same time rise from 0 to 1, to 10, to 100,
and sometimes even to 1,000 or 1,500 in the field of his microscope.
He then varied the mode of infection. He inoculated healthy worms with
the corpusculous matter, and watched the consequent growth of the
disease. He proved that 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. By their claws and their dejections, the diseased
worms spread infection. It was no hypothetical infected medium--no
problematical pythogenic gas--that killed the worms, but a definite
organism. The question of infection at a distance was also examined,
and its existence demonstrated. As might be expected from Pasteur's
antecedents, the investigation was exhaustive, 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 the important question on which he
was engaged:

*****

Place (he says) the most skilful educator, even the most expert
microscopist, in presence of large educations which present the
symptoms described in our experiments; his judgment will necessarily
be erroneous if he confines himself to the knowledge which preceded my
researches. The worms will not present to him the slightest spot of
_pebrine_; 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
carried in them the germ of the malady; ready to multiply itself
beyond measure in the chrysalides 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 corpusculous repast; an effect more
or less prompt according to the epoch of life of the worm that ha