8 THE POPULAR SCIENCE MONTHLY 



cells changed according to the conditions of fermentation. Incidentally 

 he demonstrated in alcoholic fermentation, the formation of glycerin 

 and succinic acid in addition to the well-known products alcohol and 

 carbonic acid. In short, the outcome was that Pasteur completely 

 demonstrated that the fermentations which lead to the production of 

 alcohol, vinegar, lactic acid and butyric acid are all due to the presence 

 and growth of minute organisms, or, in his own words, " The chemical 

 act of fermentation is essentially a correlative phenomenon of a vital 

 act beginning and ending with it." 



The demonstration of the part played by specific microorganisms in 

 the different fermentations was, as may readily be seen, suggestive of 

 the etiology of infectious diseases. It was in the midst of these labors 

 that the Academie des Sciences conferred upon Pasteur the Prize for 

 Experimental Physiology (for 1859), and it was Claude Bernard who 

 drew up the report and dwelt upon the " physiological tendency in 

 Pasteur's researches." Ten years before, Bernard had characterized 

 the process of fermentation as " obscure." 



The results of the investigation of fermentation led naturally to a 

 debate among the academicians concerning spontaneous generation, 

 and in this dispute Pasteur took a most important part. The older 

 examples of spontaneous generation, as, for example, the development 

 of mice from a mixture of soiled linen and cheese and of maggots from 

 decomposing meat, had long been discarded, but the demonstration 

 that fermentation and putrefaction were due to microscopic living or- 

 ganisms raised the question: Whence comes this microscopic life? Do 

 or do not these bodies arise spontaneously in putrescible and ferment- 

 able fluids? The results of several investigations were already at 

 hand. Thus Spallanzani (1769) had shown that if a putrescible fluid 

 was hermetically sealed in flasks and the flasks heated in boiling water, 

 decomposition did not occur; Schulze (1836) had obtained the same 

 result by filtering through strong solutions of acids and alkalies the air 

 which entered such flasks, as had also Schwann (1837), by first pass- 

 ing the air through heated tubes; and likewise Schroeder and Dusch 

 (1854) by filtering the air through cotton plugs. All these procedures 

 robbed the air of the suspended microorganisms and, as the fluids had 

 previously been sterilized by heat, decomposition did not occur. But 

 at the time these procedures, though now recognized as the basic prin- 

 ciples of bacteriological technique, as applied to sterilization and 

 asepsis, did not gain general credence. " Philosophic argumentation 

 always returned to the fore." The theory of spontaneous generation 

 would not down, and from 1858 to 1862 it was the most important 

 matter of debate in the discussions of the Academie des Sciences. 



Pouchet and Pasteur were the disputants, the former defendiDg the 

 thesis that " animals and plants could be generated in a medium abso- 



