The Controlling Influence of Carbon Dioxide. 145 



of this period, if taken separately, also give - 6 in either case as the average 

 value for the depressant action of C0 2 . Figs. 1 and 2 also show the return 

 to equal rates of CO2 evolution in the experiments of this series after the 

 removal of the various depressant concentrations of CO2. 



150 



o 50 100 140 



Time in hours 



Fig. 2.— The retarding effect of carbon dioxide upon anaerobic C0 2 production and the 

 recovery after the removal of C0 2 concentrations. (See Table IV and fig. \.) 



Curves A and B— Total C0 2 produced in the presence of per cent. C0 2 and 20 per 

 cent. C0 2 respectively. 



Curves C and D— Rate of C0 2 production in the presence of per cent. C0 2 and 20 per 

 cent. C0 2 respectively [cubic centimetres per 5 hours magnified 20 times]. The fluctua- 

 tions are due to laboratory temperature changes. 



The effect of C0 2 appearing thus to be constant, we must be able to express 

 in a general formula the retarding effect of different concentrations of C0 2 . 



