54 PASTEUR: THE HISTORY OF A MIND 



respects so original, and especially with Stahl, whose 

 influence on his century was so great. His was a high 

 intelligence, a powerful and generalizing mind, but he 

 believed in fencing with words, and was not a scientific 

 man. 



He introduced into his theory of fermentation, sus- 

 taining them with his great authority, ideas already 

 professed by Willis. According to Stahl, "Every sub- 

 stance in a state of putrefaction easily transmits this 

 state to another body still free from decay. Thus it is 

 that a similar body animated already by an internal 

 movement (let us bear this idea in mind for we shall 

 find it again in Liebig), may, with the greatest facility, 

 involve in the same internal movement another body 

 still in repose but disposed by nature to a similar move- 

 ment. * * * There are two periods in fermentation thus 

 considered as the result of an internal movement; in 

 the first, the different molecules of the fermenting sub- 

 stances are gently agitated, and some parts, more or less 

 attenuated, gather together; in the second, the parts 

 separate themselves from the mixture as a result of the 

 movement which animates them, and the analogous 

 parts reunite to the exclusion of the others." 



According to Stahl, the ferment intervenes only to 

 communicate its movement to the analogous parts of 

 the liquor to be fermented. Its action, therefore, we 

 should say today, is purely dynamic. Let us hasten 

 to remind ourselves once more that we must not read 

 into the phrases of the ancients our modern ideas. The 

 conception of Stahl derives its fundamental origin from 

 two classes of facts, the manufacture of bread and of 

 wine : the first a transformation arrested at its beginning, 

 during which the agitation is feeble and in which the parts 

 in the vicinity of the ferment become fermented in their 

 turn; the second characterized, on the contrary, by a 



