i2 THE POPULAR SCIENCE MONTHLY 



had recently been established by the municipality for the promotion of 

 its industries, which were largely associated with alcohol. 



Pasteur at once began the study of fermentation. This was a field 

 which lay enshrouded in darkness with the exception of one tiny ray of 

 light. In 1836, Cagniard de Latour had remarked that yeast, the fer- 

 ment of beer, was composed of cells which were capable of reproduction 

 by a sort of budding. He expressed the opinion that this microscopic 

 plant probably acted on sugar by some sort of vegetative effect. A 

 similar observation was made about the same time by Schwann, of 

 Germany. 



Pasteur set himself the problem of solving the mystery of fermen- 

 tation. His notes show that he commenced by projecting an hypothe- 

 sis associating fermentation with the dimorphism he had discovered in 

 tartaric acid, which must have been caused in some way, he thought, by 

 the action of a ferment on the grape juice. 



Berzelius, whose ideas then reigned supreme in chemistry, was of 

 the opinion that fermentation is a catalytic process. He gave it as his 

 opinion that what de Latour believed that he had seen was organic 

 matter precipitated by the process of fermentation, presenting forms 

 analogous to vegetable life. Liebig's explanation was equally mystic. 

 He defined fermentation as " action due to influence." He held the 

 opinion that a ferment is a mass of organized matter set free from 

 }east cells by their death and consequent rupture. Such matter he 

 supposed to consist of unstable molecules which in the act of changing 

 into new molecular arrangements liberated energy which in turn con- 

 verted molecules of sugar into molecules of alcohol. 



Uninfluenced by the metaphysical speculations of these great scien- 

 tists, Pasteur held to the sure road of experimentation. In August, 

 1857, he discovered the fermentative organism which sours milk and 

 produces lactic acid. The same year he was transferred to the Ecole 

 Normale Superieure at Paris. The next year he discovered that glycer- 

 ine and succinic acid are both produced simultaneously with ethel 

 alcohol when sugar is fermented. 



That Pasteur lost no implication of any phase of his researches is 

 shown by a letter to his friend Chappuis written in January, 1860. He 

 says : " I am hoping to mark a decisive step very soon in the celebrated 

 question of the spontaneous generation of life. Already I could speak ; 

 but I shall require the accuracy of an arithmetical problem. I intend 

 to attain even that." In a letter to his father, of about the same date, 

 he says : " These results open new vistas to physiology. God grant 

 that by my persevering labors I may bring a little stone to the frail and 

 ill-assured edifice of our knowledge of those deep mysteries, life and 

 death, where all our intellects have so lamentably failed." 



The belief that living creatures of both usual and unusual types are 



