ALCOHOLIC FERMENTS. 135 



BUCHNER (1885) obtained a similar result in his experiments 

 with bacteria. 



HANSEN arranged his experiments in such a way that a 

 rotatory motion was imparted to the liquid which was being 

 aerated, the cells thus being brought into continual contact with 

 the vigorous current of air which was blown through the fluid. 

 Nevertheless, there was a distinct alcoholic fermentation, and it 

 certainly follows that this was not induced by life without air. 



In NAEGELI'S "Theorie der Gariing" (1879) it is shown 

 that the admission of oxygen is highly favourable to alcoholic 

 fermentation in a sugar solution when no other nourishment is 

 present, and consequently the yeast does not multiply, or does 

 so only to a small, extent. NAEGELI therefore states (p. 26) 

 that " PASTEUR'S theory, that fermentation is induced through 

 want of oxygen, in that the yeast-cells are forced to take the 

 necessary supply of oxygen from the fermentable substance, is 

 refuted by all the facts which bear upon this question." 



A. J. BROWN, who also holds this view, made a series of 

 experiments in which fermentations were conducted in presence 

 of an abundant supply of oxygen, whilst in a duplicate set of 

 experiments conducted simultaneously, oxygen was excluded ; 

 the same number of non-multiplying yeast-cells were present 

 in both cases, and all the other conditions were kept constant. 

 These experiments showed contrary to PASTEUR'S theory 

 that the yeast-cells exercised a greater fermentative power in 

 the presence of oxygen than when the latter was excluded. 



BROWN emphasises the fact that PASTEUR'S theory rests upon 

 comparative fermentation experiments, from which he draws 

 the inference that the fermentative power of the ferment (le 

 pouvoir du ferment) that is, the proportion of the weight of 

 yeast formed to the weight of fermented sugar is very high 

 when air is excluded, and very low if air is admitted. Against 

 these experiments BROWN raises well-founded objections. 

 PASTEUR, in his determination of the fermentative power, leaves 

 out of account the duration of the fermentation (" Etudes sur 

 la biere," page 245), so that he contrasts fermentations which 

 had lasted only a few hours with those lasting several months. 

 PASTEUR states that yeast possesses great activity (activity) if 

 it has oxygen at its disposal, and that in this case it is able 



