MATILDA M. BROOKS 



181 



Fig. 2 shows the effects upon the rate of production of CO2 by 

 Bacillus hutyricus when varying amounts of NaOH are added to the 

 medium containing the bacteria at various H ion concentrations. 



Curve A shows the effect upon the rate of production of CO2 when 

 to a bacterial suspension whose pH is 7.0, sufificient NaOH is added 

 to make the pH 8.2. There is a considerable decrease in the rate 

 which becomes 21 per cent of the normal. This is followed by an 

 increase in the rate as the hydrogen ion concentration returns to 

 neutrality. 

 Rate of Co^ production 



Curve a 



Curve 6 



^ Curve C 



Cv»VE D 



Fig. 2. Curves showing the progressive eflfect of alkali upon the pH value 

 and upon the rate of production of CO2 by B. hutyricus (expressed as per 

 cent of the normal). The point marked zero on the abscissae indicates the initial 

 pll value and the rate of CO2 production of the bacteria at the instant before the 

 NaOH was added. The figure attached to the first reading indicates the pH 

 just after the addition ot acid; subsequent figures indicate the pH values at the 

 times when the readings were taken. The normal rate (which is taken as 100 

 per cent) represents a change in the pll value of the indicator tube in the apparatus 

 from 7.8 to 7.6 in a number of seconds, depending upon the amount of bacterial 

 suspension used, when the pH value of the organisms was 7.0. Each curve repre- 

 sents a single typical experiment. 



