Page:Popular Science Monthly Volume 79.djvu/16

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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 ferment 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 fermentation. His notes show that he commenced by projecting an hypothesis 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 converted molecules of sugar into molecules of alcohol.

Uninfluenced by the metaphysical speculations of these great scientists, 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 École Normale Supérieure at Paris. The next year he discovered that glycerine 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