MATILDA M. BROOKS 529 



bacteria are under normal conditions and the curve (broken line) is 

 horizontal. After this (at the point marked on the abscissa) the 

 salt is added. For example, the addition of sufficient Na taurocholate 

 to make the concentration 0.0000125 m produces a rise in the rate, 

 which remains constant during the period of experimentation. These 

 curves are selected from a number of similar typical curves, and each 

 represents one experiment. 



Rate cf COz producjlion 

 125%- 



0.005 0.01 M 



Fig. 2. Curve showing the rate of respiration of Bacillus suhtilis (expressed as 

 per cent of the normal) as affected by Na taurocholate. Normal rate as in Fig. 1. 

 Average of three experiments; probable error of the mean less than 2 per cent 

 of the mean. 



Fig. 2 shows the effects of various concentrations of sodium tauro- 

 cholate upon the rate of respiration, expressed as per cent of the nor- 

 mal rate. The rate indicated is that produced after the bacteria had 

 been in contact with the salt for 1 hour. The figure shows that sodium 

 taurocholate produces an increase in the rate at a concentration of 

 0.0000125 M and a decrease in concentrations higher than 0.000125 m. 

 It is of interest to note that the concentrations which are most favor- 

 able to the respiration of Bacillus sublilis are very dilute. The abscis- 

 sae represent the concentrations of the salts used, the ordinates repre- 

 sent the rate of respiration. 



