men of the time to have regarded these new ideas, ob-
liged as they were to reconcile their desire for the prog-
ress of science with scholastic traditions and the hatred
of innovation, so native to the practitioner. Objec-
tions occurred naturally. These remained vague to
medical men because for the most part they did not
have the laboratory spirit, but they were formulated
more clearly in the mind of Pasteur, and behold the
result!

In the first place anthrax appeared clearly to be a
contagious, inoculable disease due to something which
taken in an infinitesimal quantity from a diseased
animal could produce the disease or kill a sound animal
after a period of incubation which was evidently a period
of development and of invasion of the organism. But
what was this something? Was it the anthrax bac-
teridium, as Delafond, Davaine and Koch said? Was
it a virus, as tradition would have it--the tradition
created by what was known of smallpox, vaccine, and
sheeppox, and even by what was supposed to be known
about glanders?

The question does not seem very important to us,
who have made a choice, and who, furthermore, with
our knowledge, and without being misunderstood, are
able to give the name of virus to the anthrax bacteridium
itself. But 20 years ago the domain of viruses and
that of parasites remained separate. M. Chauveau, who
was one of the first to make a remarkable study along
this line, defined virulent diseases as contagious diseases
which were neither caused nor transmitted by a parasite.

This distinction not only seemed well founded, but
determined the direction which research was to take.
A virus could be cultivated only within the animal or-
ganism adapted to it. It could enter it in various ways
and produce in it different manifestations according

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