In 1857, a young man, Louis Pasteur, sent to the Lille Scientific Society a paper on “Lactic Acid Fermentation” and in December of the same year presented to the Academy of Sciences in Paris a paper on “Alcoholic Fermentation” in which he concluded that “the deduplication of sugar into alcohol and carbonic acid is correlative to a phenomenon of life.”  A new era in medicine dates from those two publications.  The story of Pasteur’s life should be read by every student.(*) It is one of the glories of human literature, and, as a record of achievement and of nobility of character, is almost without an equal.

     (*) Osler wrote a preface for the 1911 English edition of the
     Life by Vallery-Radot.—­Ed.

At the middle of the last century we did not know much more of the actual causes of the great scourges of the race, the plagues, the fevers and the pestilences, than did the Greeks.  Here comes Pasteur’s great work.  Before him Egyptian darkness; with his advent a light that brightens more and more as the years give us ever fuller knowledge.  The facts that fevers were catching, that epidemics spread, that infection could remain attached to articles of clothing, etc., all gave support to the view that the actual cause was something alive, a contagium vivum.  It was really a very old view, the germs of which may be found in the Fathers, but which was first clearly expressed—­so far as I know—­by Fracastorius, the Veronese physician, in the sixteenth century, who spoke of the seeds of contagion passing from one person to another;(12) and he first drew a parallel between the processes of contagion and the fermentation of wine.  This was more than one hundred years before Kircher, Leeuwenhoek and others began to use the microscope and to see animalcula, etc., in water, and so give a basis for the “infinitely little” view of the nature of disease germs.  And it was a study of the processes of fermentation that led Pasteur to the sure ground on which we now stand.

     (12) Varro, in De Re Rustica, Bk.  I, 12 (circa 40 B.C.), speaks
     of minute organisms which the eye cannot see and which enter the
     body and cause disease.

Out of these researches arose a famous battle which kept Pasteur hard at work for four or five years—­the struggle over spontaneous generation.  It was an old warfare, but the microscope had revealed a new world, and the experiments on fermentation had lent great weight to the omne 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