of the silkworm is, in every respect, comparable to the
cholera among mankind. But it differs from the cholera, and so far is a
more formidable malady, in being hereditary, and in being, under some
circumstances, contagious as well as infectious.

[Footnote 11: _Etudes sur les Maladies actuelles des Vers a Soie_, p.
53.]

The Italian naturalist, Filippi, discovered in the blood of the silkworms
affected by this strange disorder a multitude of cylindrical corpuscles,
each about 1/6000th of an inch long. These have been carefully studied by
Lebert, and named by him _Panhistophyton_; for the reason that in
subjects in which the disease is strongly developed, the corpuscles swarm
in every tissue and organ of the body, and even pass into the undeveloped
eggs of the female moth. But are these corpuscles causes, or mere
concomitants, of the disease? Some naturalists took one view and some
another; and it was not until the French Government, alarmed by the
continued ravages of the malady, and the inefficiency of the remedies
which had been suggested, despatched M. Pasteur to study it, that the
question received its final settlement; at a great sacrifice, not only of
the time and peace of mind of that eminent philosopher, but, I regret to
have to add, of his health.

But the sacrifice has not been in vain. It is now certain that this
devastating, cholera-like, Pebrine, is the effect of the growth and
multiplication of the _Panhistophyton_ in the silkworm. It is contagious
and infectious, because the corpuscles of the _Panhistophyton_ pass away
from the bodies of the diseased caterpillars, directly or indirectly, to
the alimentary canal of healthy silkworms in their neighbourhood; it is
hereditary because the corpuscles enter into the eggs while they are
being formed, and consequently are carried within them when they are
laid; and for this reason, also, it presents the very singular
peculiarity of being inherited only on the mother's side. There is not a
single one of all the apparently capricious and unaccountable phenomena
presented by the Pebrine, but has received its explanation from the fact
that the disease is the result of the presence of the microscopic
organism, _Panhistophyton_.

Such being the facts with respect to the Pebrine, what are the
indications as to the method of preventing it? It is obvious that this
depends upon the way in which the _Panhistophyton_ is generated. If it
may be generated by Abiogenesis,