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III. Pasteur and the Era of Bacteriology
THE story of bacteriology can best be told by recounting the labors of Pasteur, for while bacteria were known and theories of infection had been elaborated and vaccination practised before his time, it was he who definitely established the importance of bacteria in putrefaction, fermentation and disease, and gave to vaccination a scientific basis. The influence of these labors is compatible in medicine only to that of Virchow in his field and is as great as that exerted in general biology by Darwin's researches. The story of rapid sequence of Pasteur's brilliant discoveries in science, each of crucial importance and establishing a new principle have, I believe, no parallel in biology or, for that matter, any other science.
But before presenting Pasteur's labors it is necessary to outline the knowledge of bacteria and the theories of fermentation, infection and allied processes which were current at the beginning of his era.
Bacteria were first seen by Leeuwenhoek, a Dutch lens-maker in 1673. This was long before the day of the compound microscope, but Leeuwenhoek was able to make such excellent short focus single lenses that he could study red blood corpuscles and spermatozoa, detect minute globular particles in yeast, and, as we know from his drawings, even discover some of the larger microorganisms in the tartar of the teeth, in saliva and intestinal and other fluids. In 1838, about the time of the development of the compound microscope, Ehrenberg attempted a classification of bacteria based on sixteen species. Our exact knowledge, however, begins with Cohn's studies which extended from 1853 to 1875, and were the first to differentiate between the spherical forms
- The Hitchcock lectures, delivered at the University of California, January 23-26, 1912.