ACTION OF FERMENTS. 725 



may still remain in the liquid, does not suffer change from 

 contact with the newly-deposited yeast, but retains all the 

 characters of gluten. 



Yeast is a product of the decomposition of gluten ; but it 

 passes into a second stage of decomposition when in contact 

 with water. On account of its being in this state of further 

 change, yeast excites fermentation in a fresh solution of sugar, 

 and if this second saccharine fluid should contain gluten, (should 

 it be wort, for example,) yeast is again generated in consequence 

 of the transposition of the elements of the sugar exciting a 

 similar change in this gluten. 



After this explanation, the idea that yeast reproduces itself 

 as seeds reproduce seeds, cannot for a moment be entertained".* 



To these may be added the results of the very recent in- 

 quiries of MM. Boutron and Fremy on the phenomena of the 

 fermentation of malt. These chemists find that the same azo- 

 tised matter in the grain, which acts as the ferment, passes 

 through a succession of changes, and can excite different kinds 

 of fermentation at different stages in the progress of its decom- 

 position ; that it is not one but a series of ferments. It is as 

 diastase that it first appears, or this is the first condition of the 

 ferment in the infusion of malt, as is proved by the action 

 which it exerts upon starch, the latter being converted into 

 sugar. From the acidity of the liquor which is afterwards 

 observed, it is evident that the azotised matter next takes the 

 character of the lactic ferment (page 808), and converts the 

 sugar, to a certain extent, into lactic acid. A period then 

 arrives at which the liquid, still transparent, becomes turbid, 

 and the resulting precipitate is the matter which can produce 

 the alcoholic fermentation ; and it is only at this epoch that 

 alcohol is formed and carbonic acid disengaged. That it is the 

 insoluble precipitate to which the alcoholic fermentation should 

 be ascribed, is proved by filtering the liquid to separate the 

 ferment, when the alcoholic fermentation is immediately 

 arrested.f 



The action of yeast and all other ferments is destroyed by the 



* Liebig's Organic Chemistry in its .applications to Agriculture and Physiology, 

 edited by Dr. Lyon Playfair. 



f Ann. de China. &c. 3 serie, t. 2, p. 261). 



