on of vinegar, he became more and more convinced that these
studies on fermentation had given him the key to the nature of the
infectious diseases. It is a remarkable fact that the distinguished
English philosopher of the seventeenth century, the man who more
than anyone else of his century appreciated the importance of the
experimental method, Robert Boyle, had said that he who could discover
the nature of ferments and fermentation, would be more capable than
anyone else of explaining the nature of certain diseases.

In 1876 there appeared in Cohn's "Beitrage zur Morphologie der Pflanzen"
(II, 277-310), a paper on the "AEtiology of Anthrax" by a German
district physician in Wollstein, Robert Koch, which is memorable in our
literature as the starting point of a new method of research into
the causation of infectious diseases. Koch demonstrated the constant
presence of germs in the blood of animals dying from the disease. Years
before, those organisms had been seen by Pollender and Davaine, but
the epoch-making advance of Koch was to grow those organisms in a pure
culture outside the body, and to produce the disease artificially
by inoculating animals with the cultures Koch is really our medical
Galileo, who, by means of a new technique,--pure cultures and isolated
staining,--introduced us to a new world. In 1878, followed his study on
the "AEtiology of Wound Infections," in which he was able to demonstrate
conclusively the association of micro-organisms with the disease. Upon
those two memorable researches made by a country doctor rests the modern
science of bacteriology.

The next great advance was the discovery by Pasteur of the possibility
of so attenuating, or weakening, the poison that an animal inoculated
had a slight attack, recovered and was then protected against the
disease. More than eighty years had passed since on May 14, 1796, Jenner
had vaccinated a child with cowpox and proved that a slight attack of
one disease protected the body from a disease of an allied nature. An
occasion equally famous in the history of medicine was a day in 1881,
when Pasteur determined that a flock of sheep vaccinated with the
attenuated virus of anthrax remained well, when every one of the
unvaccinated infected from the same material had died. Meanwhile, from
Pasteur's researches on fermentation and spontaneous generation, a
transformation had been initiated in the practice of surgery, which,
it is not too much to say, has pro