370 



STUDIES ON FERMENTATION. 



combination would have been scarcely appreciable in absence 

 of yeast. It follows, therefore, that the oxygen in solution is 

 taken up by the yeast, under the conditions of which we are 

 speaking. This has been proved directly by an experiment. 



Ch 1f. i 



A double quantity of j'^east was employed for a tun similar to 

 the preceding one, and it was found that the oxygen in solution 

 disappeared completely in less than half the time that it took 

 to disappear in the first case.* It is very important to notice 

 that in our 32-hectolitre tun, at the moment when we deter- 

 mined the complete disappearance of the oxygen in solution, 

 the cells of yeast had assumed a younger and fuller appearance 

 than they had at first ; but they had not multiplied at all up to 



* Wo kuow also from the direct experiments of M. Schiitzenberger, 

 performed on aerated -n'ater with which yeast had been mixed, that yeast 

 causes all the oxygen in solution to disappear very quicklj-, so that 

 hydrosulphite gives no evidence of a trace. (See ScnuxzENBERGER, 

 Eevue scientijique, vol. iii. (2), Aj-iril, 1874). 



