NEW CONCEPTIONS IN SCIENCE 



This conception, which represents the very latest 

 results in biology, has, as any one might guess, 

 not been reached at a bound. It has been gained 

 by very slow steps. And incidentally this advance 

 has served to show that fermentation, which once 

 seemed so comparatively simple, is in reality a 

 wonderful thing. Positive knowledge runs back 

 only about sixty years. The beginning was with a 

 French crystallographer. Not many, perhaps, will 

 recognize under this designation the great bacteri- 

 ologist Pasteur, to whom we owe the whole germ 

 theory of disease. Yet it was precisely his studies 

 of fermentation which led him to his immortalizing 

 discovery of microbes ; and it was, in turn, his study 

 of crystals which led him to the study of fermenting 

 malt. 



Pasteur started out to be a chemist. He took up 

 the puzzling question of why one sort of tartaric 

 acid, in solution, will twist a beam of light out of a 

 straight path to the right, another sort to the left. 

 One day he chanced to observe that a certain kind 

 of yeast-cells would thrive in the one medium, not 

 in the other ; this seemed to indicate that the struct- 

 ure of the living yeast-plant was closely related to 

 the queer actions of his right- and left-handed acids. 



When, forty years later, that most fruitful ca- 

 reer in the last century had closed, Pasteur and 

 those who followed his lead had gone deviously 



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