ENSILAGE AND FERMENTATION. 223 



The weights as applied gave a uniform pressure ; but the cover, as 

 will be seen from the table, did not settle at a uniform rate. There 

 was a fall of 5° in temperature during the first three days, then fol- 

 lowed a gradual but not uniform rise, until the maximum of 87° was 

 reached at the end of the first week. It will likewise be noticed that 

 a variation of but 5° from the initial temperature occurred during the 

 first three weeks after the cover was put on and weighted, and that 

 the fall in the temperature was not uniform. 



Experiments were repeatedly made with samples of ensilage, taken 

 through the tube, from the interior of the silo. The samples obtained 

 on the 9th of September swarmed with bacteria, which were remark- 

 ably active and rapidly increasing by self-division. After the first few 

 days the indications of rapid reproduction were not so marked, but the 

 activity of the bacteria was not sensibly diminished until the temper- 

 ature had fallen below 60°, more than two months after the silo was 

 filled. The variations in temperature and in the rate of settling were 

 undoubtedly connected with the vital activity of the bacteria, but the 

 precise relation of these variations could not be traced. 



The real significance of these minute organisms can not be fully 

 appreciated without a review, including a brief history, of the known 

 facts of the process of 



Fermej^tatio:?^. — The alchemists were acquainted with ferments 

 and fermentation as early as the thirteenth century, but we need not 

 stop to notice their crude theories in regard to the process. In 1659, 

 Willis, an English physician, presented a theory of fermentation, which 

 was revived by Stahl, the originator of the phlogiston theory, in 1697. 

 According to the theory of these philosophers, ferments had a peculiar 

 motion of their particles which they communicated to the particles of 

 fermentable substances and thus produced fermentation. The discov- 

 ery of carbonic acid by Black (1752), of oxygen by Priestley (1774), 

 and of the composition of the atmosphere and water by Cavendish 

 (1781), laid the foundation for the experiments of Lavoisier, who at- 

 tempted a quantitative determination of the changes taking place in 

 the transformation of sugar into alcohol. Gay-Lussac (1815) revised 

 the figures obtained by Lavoisier, by less perfect methods, and made 

 a close approximation to a correct formula. In 1828 Dumas and Boul- 

 lay pointed out and corrected errors in the formulae of Gay-Lussac, 

 and in this amended form they were, for many years, accepted as an 

 accurate statement of the phenomena of alcoholic fermentation. After- 

 ward, however, the discovery was made that glycerine and succinic 

 acid are constant products of the process, and the formulae had to be 

 again corrected. These formulae, even in their amended form, did not 

 take into the account the yeast which had been recognized as an essen- 

 tial element in the process, and theories were formed to account for 

 its action. Berzelius attributed the influence of yeast to a " catalytic " 

 action — mere contact with the ferment being sufficient to excite fer- 



