254 STUDIES ON FERMENTATION. 



on its vital processes after the manner of an ordinary fungus ; the 

 mode of life, that is, in which the ratio between the weight of 

 sugar decomposed and the weight of the new cells produced will 

 be the same as holds generally among organisms which are not 

 ferments. In short, varying our form of expression a little, we 

 may conclude with perfect truth, from the sum total of observed 

 facts, that the yeast which lives in the presence of oxygen and 

 can assimilate as much of that gas as is necessary to its perfect 

 nutrition, ceases absolutely to be a ferment at all. Nevertheless, 

 yeast formed under these conditions and subsequently brought 

 into the presence of sugar, out of the influence of air, would de- 

 compose more in a given time than in any other of its states. 

 The reason is that yeast which has formed in contact with air, 

 having the maximum of free oxygen that it can assimilate, is 

 fresher and possessed of greater vital activity than that which 

 has been formed without air or with an insufificiency of air. M. 

 Schiitzenberger would associate this activity with the notion 

 of time in estimating the power of the ferment ; but he forgets 

 to notice that yeast can only manifest this maximum of energy 

 under a radical change of its life-conditions ; by having no 

 more air at its disposal and breathing no more free oxygen. 

 In other words, when its respiratory power becomes null, its 

 fermentative power is at its greatest. M. Schiitzenberger 

 asserts exactly the opposite (p. 151 of his work — Paris, 1875),* 

 and so gratuitously places himself in opposition to facts. 

 In presence of abundant air-supply, yeast vegetates with 



extraordinary activity. AVe see this in the weight of new 

 yeast, comparatively large, that may be formed in the course 



* Page 182, English edition. 



