266 Prof. Potter. Electrical Effects accompanying the [July 14, 



It is interesting to note that after the maximum voltage has been attained 

 there is always a slight drop in the curve, which was not so pronounced 

 following the more gradual rise at the lower temperature. 



When cells were maintained at a temperature of 50° C. there was no 

 deflection of the galvanometer, and when the temperature was lowered to 

 25° C. there was again no electric effect, showing that the vitality of the 

 yeast had been destroyed. At 0° C. no deflection could be detected, but 

 when the temperature of these cells was gradually raised by placing the cell 

 in an incubator, a voltage was soon observed which continued to increase as 

 the temperature became more favourable. At the freezing point therefore 

 the yeast was not killed, and the absence of electrical action at this tempera- 

 ture shows an effect of suspended animation. 



















Fig- 4 











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io 20 30 40 so 60 Time 70 in 8ominures9o ioo 



Curves showing E.M.F. developed at different temperatures. 5 grm. of yeast added in each case to a 

 10-per-cent. solution of glucose. I, initial temperature 25° C. ; II, initial temperature 17° C. ; 

 III, initial temperature 10° C. 



It should be mentioned that the initial temperature of the fermenting 

 solution does not remain constant, but gradually changes as the process of 

 fermentation proceeds. 



These results demonstrate that the E.M.F. developed can only be 

 attributed to the fermentative action of the yeast, and the electrical effects 

 are the measure of the activity of the yeast. It has been shown that the 

 character of the culture medium modifies to a great extent the electrical 

 effects produced, and degrees of concentration which are too high for the 

 favourable growth of the yeast are reflected in the diminution of the voltage 

 registered and a much reduced speed of reaction. Further, the speed of 

 reaction varies with the amount of active yeast present in the cells, and the 

 gradient of the curve is directly influenced by this factor, being much steeper 



