2,64 STUDIES ON FERMENTATION. 



character of this yeast, nevertheless, continues, and produces 

 even increased effects, if it is made to act on sugar apart from 

 the influence of free oxygen. 



" It seems, therefore, natural to admit that when yeast 

 functions as a ferment by living apart from the influence of 

 air, it derives oxygen from the sugar, and that this is the 

 origin of its fermentative character. 



" M. Pasteur explains the fact of the immense activity at 

 the commencement of fermentations by the influence of the 

 oxygen of the air held in solution in the liquids, at the time 

 when the action commences. The author has found, moreover, 

 that the yeast of beer sown in an albuminous liquid, such as 

 yeast-water, still multiplies, even when there is not a trace of 

 sugar in the liquid, provided always that atmospheric oxygen 

 is present in large quantities. When deprived of air, under 

 these conditions, yeast does not germinate at all. The same 

 experiments may be repeated with albuminous liquid, mixed 

 with a solution of non- fermentable sugar, such as ordinary 

 crystallized milk-sugar. The results are precisely the same. 



" Yeast formed thus in the absence of sugar does not change 

 its nature ; it is still capable of causing sugar to ferment, if 

 brought to bear upon that substance apart from air. It must 

 be remarked, however, that the development of yeast is effected 

 with great difficulty when it has not a fermentable substance 

 for its food. In short, the yeast of beer acts in exactly the same 

 manner as an ordinary plant, and the analogy would be com- 

 plete if ordinary plants had such an affinity for oxygen as 

 permitted them to breathe by appropriating this element from 

 unstable compounds, in which case, according to M. Pasteur, 

 they would appear as ferments for those substances. 



" M. Pasteur declares that he hopes to be able to realize this 

 result, that is to say, to discover the conditions under which 

 certain inferior plants may live apart from air in the presence 

 of sugar, causing that substance to ferment as the yeast of beer 

 would do." 



This summary and the preconceived views that it set forth 



