MATILDA M. BROOKS 



197 



from 8.3 to 8.1. The rate is taken as the reciprocal of the time re- 

 quired to change the pH value from 8.3 to 8.1. The curve shows a 

 gradual increase in respiration as the concentration of ether in- 

 creases. The curve rises more rapidly from 2.9 to 5.84 per cent, and 

 very rapidly near 7.3 per cent. In fact, the change in pH value at 

 7.3 per cent is almost instantaneous. 



B.ATE. 



sooo-f ' 



ioo-( ;^ -o o 



10 AflNU TES 



Fig. 2. Curves showing the effect of 7.3 per cent ether on the rate of respira- 

 tion of B. suhtilis. Dotted hne, control. The normal rate (which is taken as 100 

 per cent) corresponds to a change from pH 8.3 to pH 8.1 in 7 minutes. Average 

 of three experiments. 



For the sake of comparison, a similar series of observations was 

 made with the same concentrations of ether dissolved in 0.85 per 

 cent NaCl. Curve 2 of Fig. 4 shows increase in respiration with 

 increase in concentration; the curve rises rapidly at first, then more 

 slowly and finally quite steeply. No sudden outpouring of CO2 is 

 observed in 7.3 per cent ether as is the case in the tap water (Curve 

 1). This seems to indicate an antagonism between the action of 

 NaCl and ether. 



