vivum
ex ovo doctrine. The famous Italians, Redi and Spallanzani, had led the
way in their experiments, and the latter had reached the conclusion
that there is no vegetable and no animal that has not its own germ. But
heterogenesis became the burning question, and Pouchet in France, and
Bastian in England, led the opposition to Pasteur. The many famous
experiments carried conviction to the minds of scientific men, and
destroyed forever the old belief in spontaneous generation. All along,
the analogy between disease and fermentation must have been in Pasteur's
mind; and then came the suggestion, "What would be most desirable is to
push those studies far enough to prepare the road for a serious
research into the origin of various diseases." If the changes in lactic,
alcoholic and butyric fermentations are due to minute living organisms,
why should not the same tiny creatures make the changes which occur
in the body in the putrid and suppurative diseases? With an accurate
training as a chemist, having been diverted in his studies upon
fermentation into the realm of biology, and nourishing a strong
conviction of the identity between putrefactive changes of the body
and fermentation, Pasteur was well prepared to undertake investigations
which had hitherto been confined to physicians alone.

So impressed was he with the analogy between fermentation and the
infectious diseases that, in 1863, he assured the French Emperor of
his ambition "to arrive at the knowledge of the causes of putrid and
contagious diseases." After a study upon the diseases of wines, which
has had most important practical bearings, an opportunity arose which
changed the whole course of his career, and profoundly influenced the
development of medical science. A disease of the silkworm had, for some
years, ruined one of the most important industries in France, and in
1865 the Government asked Pasteur to give up his laboratory work and
teaching, and to devote his whole energies to the task of investigating
it. The story of the brilliant success which followed years of
application to the problem will be read with deep interest by every
student of science. It was the first of his victories in the application
of the experimental methods of a trained chemist to the problems
of biology, and it placed his name high in the group of the most
illustrious benefactors of practical industries.

In a series of studies on the diseases of beer, and on the mode of
producti