THE 



POPULAR SCIENCE 



MONTHLY. 



JULY, 1912 

 EESEARCH IN MEDICINE 1 



Bt Professor RICHARD M. PEARCE 



UNIVERSITY OF PENNSYLVANIA 



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 infec- 

 tion 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 medi- 

 cine 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 knowl- 

 edge, however, begins with Cohn's studies which extended from 1853 

 to 1875, and were the first to differentiate between the spherical forms 



1 The Hitchcock lectures, delivered at the University of California, January 

 23-26, 1912. 



