320 STUDIES ON FERMENTATIOX. 



grammes of sugar in six da3's, at the end of which time it was 

 exhausted. The soluble portion of a like quantity of 5 grammes 

 of the same yeast caused the fermentation of 10 grammes of 

 sugar in nine days, after which the yeast developed by the 

 sowing was likewise exhausted." 



How is it possible to maintain that, in the fermentation of 

 water containing nothing but sugar, the soluble portion of the 

 yeast does not act, either in the production of new globules or 

 the perfection of old ones, when we see, in the preceding expe- 

 riment, that after this nitrogenous and mineral portion has been 

 removed bj'' boiling, it immediately serves for the production of 

 new globules, which, under the influence of the sowing of a 

 mere trace of globules, causes the fermentation of much 

 sugar?* 



In short, Liebig is not justified in saying that the solution of 

 pure sugar, caused to ferment by means of yeast, contains none 

 of the elements needed for the growth of yeast, neither nitrogen, 

 sulphur, nor phosphorus, and that, consequently, it should not 

 be possible, by our theory, for the sugar to ferment. On the 

 contrar}^ the solution does contain all these elements, as a 

 consequence of the introduction and presence of the yeast. 



Let us proceed with our examination of Liebig's criticisms : — 



" To this," he goes on to say, " must be added the decompos- 

 ing action which yeast exercises on a great number of substances, 



* It is important that we should here remark that, in the fermentation 

 of pure solution of sugar by means of j-east, the oxygen originally dis- 

 solved in the water, as well as that appropriated by the globules of yeast 

 in their contact with air, has a considerable effect on the activity of 

 fermentation. As a matter of fact, if we pass a strong current of car- 

 bonic acid through the sugared water and the water in which the yeast 

 has been treated, the fermentation will be rendered extremely sluggish, 

 and the few new cells of yeast which f<n-m will assume strange and 

 abnormal aspects. Indeed this might have been expected, for we have 

 seen that yeast, when somewhat old, is incapable of development or of 

 causing fermentation, even in a fermentable medium containing all the 

 nutritive principles of yeast, if the liquid has been deprived of air ; much 

 more should we expect this to be the case in pure sugared water, like- 

 wise deprived of air. 



