SECOND PART 

 LACTIC AND ALCOHOLIC FERMENTATIONS 



THE KNOWLEDGE OF FERMENTATIONS BEFORE 

 LAVOISIER 



At the time Pasteur approached it, the question of 

 fermentations formed such a confused mass that not only 

 is it difficult to picture to ourselves what the chemists 

 of the epoch thought of it but we doubt even whether 

 they had any clear idea of it, we find so many con- 

 tradictions and singular statements in their writings. 

 When we seek to discover whence came that embryonic 

 notion respecting fermentation, persistent to the middle 

 of the nineteenth century, we see that it was due not to 

 the difficulties of the subject, but to the fact that the 

 question had been a philosophical one before it became 

 a scientific one. 



The phenomena of fermentation are as old as the 

 world, and the first that man learned to control and to 

 adapt to his needs are probably those which lead to the 

 production of bread and wine. More time and effort 

 doubtless was required to procure beer. Once found, 

 it was inevitable that the methods which yielded these 

 articles of food and drink should spread rapidly and 

 soon become common. The bubbling which takes 

 place spontaneously in the mass of vintage, or which is 

 produced in the barley wort by the addition of the yeast 

 of beer, the change of savor and texture which result 

 from the introduction of yeast into the flour paste are 



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