78 CRITIQUES AND ADDRESSES. [iv. 



However this may be, there can be no doubt that the 

 constituent elements of fully 98 per cent, of the sugar 

 which has vanished during fermentation have simply 

 undergone rearrangement ; like the soldiers of a brigade, 

 who at the word of command divide themselves into 

 the independent regiments to which they belong. The 

 brigade is sugar, the regiments are carbonic acid, succinic 

 acid, alcohol, and glycerine. 



From the time of Fabroni, onwards, it has been ad- 

 mitted that the agent by which this surprising rearrange- 

 ment of the particles of the sugar is effected is the yeast. 

 But the first thoroughly conclusive evidence of the 

 necessity of yeast for the fermentation of sugar was 

 furnished by Appert, whose method of preserving perish- 

 able articles of food excited so much attention in France 

 at the beginning of this century. Gay-Lussac, in his 

 "Memoire sur la Fermentation/' 1 alludes to Appert' s 

 method of preserving beer-wort unfermented for an 

 indefinite time, by simply boiling the wort and closing 

 the vessel in which the boiling fluid is contained, in such 

 a way as thoroughly to exclude air ; and he shows that, 

 if a little yeast be introduced into such wort, after it 

 has cooled, the wort at once begins to ferment, even 

 though every precaution be taken to exclude air. And 

 this statement has since received full confirmation from 

 Pasteur. 



On the other hand, Schwann, Schroeder and Dusch, 

 and Pasteur, have amply proved that air may be allowed 

 to have free access to beer-wort, without exciting 

 fermentation, if only efficient precautions are taken 

 to prevent the entry of particles of yeast along with 

 the air. 



Thus, the truth that the fermentation of a simple 

 solution of sugar in water depends upon the presence of 



1 " Aimales de Cliimie," 1810. 



