the cause of the disease. That is the idea divested of all
its trappings--an idea reached ordinarily only after
one has made the tour of ideas much more complicated.
In fact, as we shall see, Pasteur reached this conclusion
only, so to speak, in spite of himself, and after two years
of study.

He was, it seems, more disposed to believe at this
moment that the disease, whatever it might be, could
by modifying the fluids of the body prepare the soil
for this or that microbe, which was then according to the
case, either the result of the disease, or the visible evi-
dence of it, or the beginning of a new disease. We shall
see later that these notions are not as exclusive of the
other idea as one might at first sight believe them to be.
In all cases, they ended with a repercussion of the microbe
on its host, and it was for this reason that Pasteur main-
tained for so long a time the relations between the phy-
siology of the ferments and that of the higher animals.
Thus we have seen him liken the red blood-corpuscle
to the acetic ferment which, like the latter, can take
the oxygen from the air and carry it, endowed with a
more powerful activity, to the combustible substance.

But when there was raised the question of going farther
and of actually coming into contact with the higher
animals, Pasteur hesitated. He was not a physiologist.
To no purpose did we go to hear the course of Claude
Bernard, where he took notes feverishly. It would have
been necessary for him to become a new soul, and he had
neither the time for it nor the patience. The insist-
ance of Dumas had just placed him face to face with
an experience which he both desired and dreaded, and
if his self-distrust had made him hesitate, at the first
encounter, in reality, the attraction for the unknown and
a certain interior voice urged him to accept.

Consequently, his decision was soon made. After

-146-