NINETEENTH-CENTURY MEDICINE 



a vastly more important r61e in the economy of nature 

 than any one previously had supposed. They held, for 

 example, that the minute specks which largely make 

 up the substance of yeast are living vegetable organ- 

 isms, and that' the growth of these organisms is the 

 cause of the important and familiar process of fermen- 

 tation. They even came to hold, at least tentatively, 

 the opinion that the somewhat similar micro-organ- 

 isms to be found in all putrefying matter, animal or 

 vegetable, had a causal relation to the process of putre- 

 faction. 



This view, particularly as to the nature of putrefac- 

 tion, was expressed even more outspokenly a little later 

 by the French botanist Turpin. Views so supported 

 naturally gained a following; it was equally natural 

 that so radical an innovation should be antagonized. 

 In this case it chanced that one of the most dominating 

 scientific minds of the time, that of Liebig, took a firm 

 and aggressive stand against the new doctrine. In 

 1839 he promulgated his famous doctrine of fermenta- 

 tion, in which he stood out firmly against any " vital- 

 istic" explanation of the phenomena, alleging that the 

 presence of micro-organisms in fermenting and putre- 

 fying substances 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 con- 

 firmed, but later ones contradicted, the observations of 

 Schwann, and this combined authority gave the vital- 

 istic conception a blow from which it had not rallied at 

 the time when Pasteur entered the field. Indeed, it 

 was currently regarded as settled that the early stu- 



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