CENTURY'S PROGRESS IN SCIENTIFIC MEDICINE 



which he stood out firmly against any " vitalistic " ex- 

 planation of the phenomena, alleging that the presence 

 of micro-organisms in fermenting and putrefying sub- 

 stances was merely incidental, and in no sense causal. 

 This opinion of the great German chemist was in a 

 measure substantiated by experiments of his compatriot 

 Helmholtz, whose earlier experiments confirmed, but 

 later ones contradicted, the observations of Schwann, 

 and this combined authority gave the vitalistic concep- 

 tion a blow from which it had not rallied at the time 

 when Pasteur entered the field. Indeed, it was current- 

 ly regarded as settled that the early students of the 

 subject had vastly overestimated the importance of mi- 

 cro-organisms. 



o 



And so it came as a new revelation to the generality of 

 scientists of the time, when, in 1857 and the succeeding 

 half-decade, Pasteur published the results of his re- 

 searches, in which the question had been put to a series 

 of altogether new tests, and brought to unequivocal 

 demonstration. 



He proved that the micro-organisms do all that his 

 most imaginative predecessors had suspected, and more. 

 Without them, he proved, there would be no fermenta- 

 tion, no putrefaction no decay of any tissues, except by 

 the slow process of oxidation. It is the microscopic 

 yeast plant which, by seizing on certain atoms of the 

 molecule, liberates the remaining atoms in the form of 

 carbonic acid and alcohol, thus effecting fermentation; 

 it is another microscopic plant a bacterium, asDevaine 

 had christened it which in a similar way effects the 

 destruction of organic molecules, producing the condi- 

 tion which we call putrefaction. Pasteur showed, to 

 the amazement of biologists, that there are certain forms 



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