The Evolution of Bacteriology 21 



of his view." "He seems quite aware of the gravity of 

 the matter at hand ; this is his deliberate and almost solemn 

 appeal: 'With the view of settling these questions, there- 

 fore, we may carefully prepare an infusion from some 

 animal tissue, be it muscle, kidney, or liver; we may place 

 it in a flask whose neck is drawn out and narrowed in the 

 blowpipe flame; we may boil the fluid, seal the vessel during 

 ebullition, and, keeping it in a warm place, may await the 

 result, as I have often done. . . . After a variable 

 time the previously heated fluid within the hermetically 

 sealed flasks swarms more or less plentifully with bacteria 

 and allied organisms, even though the fluids have been 

 much degraded in quality by exposure to the temperature 

 of 212 F., and have in all probability been rendered far 

 less prone to engender independent living units than the 

 unheated fluids in the tissues would be.' ' 



II. CHEMIC CONTRIBUTIONS ; FERMENTATION AND PUTREFACTION. 



As in the world of biology the generation of life was an 

 all-absorbing problem, so in the world of chemistry the 

 phenomena of fermentation and putrefaction were inex- 

 plicable so long as the nature of the ferments was not 

 understood. 



In the year 1837 La tour and Schwann succeeded in 

 demonstrating that the minute oval bodies which had been 

 observed in yeast since the time of Leeuwenhoek were 

 living organisms vegetable forms capable of growth. 



So long as yeast was looked upon as an inert substance 

 it was impossible to understand how it could impart fer- 

 mentation to other substances; but when it was shown 

 by Latour that the essential element of yeast was a growing 

 plant, the phenomenon became a perfectly natural conse- 

 quence of life. Not only the alcoholic, but also the acetic, 

 lactic, and butyric fermentations have been shown to re- 

 sult from the energy of low forms of vegetable life, chiefly 

 bacterial in nature. Prejudice, however, prevented many 

 chemists from accepting this view of the subject, and 

 Liebig strenuously adhered to his theory that fermenta- 

 tion was the result of the internal molecular movements 

 which a body in the course of decomposition communicates 

 to other matter whose elements are connected by a very 

 feeble affinity. 



Pasteur was the first to prove that fermentation is an 



