AEROBIC LIFE OF ANAEROBIC SPECIES 203 



has at its disposal for its needs the oxygen dissolved 

 in the liquid, and a little free oxygen in the air of the 

 flask. This time life is more active, fermentation more 

 rapid, reproduction of the yeast more abundant, and 

 for 100 grams of sugar transformed we have about 

 1.5 grams of yeast produced. 



Fig. 17. Left side: disjointed cells of old yeast. Right side: Their re- 

 juvenation in a sugared must. 



Let us go a step further in the process of aeration. 

 Let us spread out our sugar solution over a broad 

 surface or shake it in contact with air, so that each 

 yeast cell finds itself constantly in contact with the 

 free oxygen of which it has need. This time, the sugar 

 disappears rapidly; it no longer gives alcohol, or at 



