196 



STUDIES ON RESPIRATION. Ill 



cent. For example, the curve readily shows that 7.3 per cent ether, 

 although causing a rapid respiration at first, does not produce a lower 

 pH value than 7.9. After allowing these tubes to stand several days, 

 they change about 0.2 pH unit, or reach 7.7 pH, owing probably to the 

 fact that there are a few surviving organisms that are perhaps more 

 resistant than the majority, as later experiments indicate. 



PH 







100 



200 MIN 



Fig. 1. Curves showing the effects of various concentrations of ether on the 

 respiration of B. suhtilis. Dotted line, control. Average of two experiments. 



The figures expressing the per cent of ether should be corrected by multiplying 

 by 0.73. 



Fig. 2 shows more readily the effect of 7.3 per cent ether upon the 

 rate of respiration as compared with the normal rate (dotted line). 

 There is a sudden outpouring of CO2 followed by cessation of 

 respiration. 



Fig. 3 plotted in the same way, shows the effect of lower concen- 

 trations of ether upon the rate of respiration as compared with the 

 normal curve (dotted line). 



Curve 1 in Fig. 4 shows the rate of respiration in various concen- 

 trations of ether during the first interval in which the pH value changes 



