MATILDA M. BROOKS U 



Fig. 3 shows the manner in which the rate of CO2 production 

 changes under the influence of KCl in concentrations of 0.2, 0.3, 

 and 1.0 M. When the concentration is 0.2 m, there is an increase 

 in the rate which remains constant for some time; in lower concen- 

 trations (0.15 and 0.1 m) the rate is normal, while in higher con- 

 centrations there is a decrease in rate. These curves are selected 

 from a number of similar typical curves, and each represents one 

 experiment. 



Fig. 4 shows the effects of various concentrations of NaCl, KCl, 

 and CaCl2 upon the rate of respiration expressed as per cent of the 

 normal rate. The rate indicated is that produced after the bacteria 

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

 NaCl produces an increase in the rate of respiration at a concentration 

 of 0.15 M, In 0.5, 0.8, and 1.0 m there is a decrease. KCl pro- 

 duces an increase in the rate at a concentration of 0.2 m, and in con- 

 centrations higher than 0.3 m it causes a decrease. CaCl2 causes an 

 increase in the rate at a concentration of 0.05 m and in concentrations 

 higher than 0.1 m it causes a decrease in respiration. CaCl2 is the 

 most toxic of the salts used, while KCl is the least toxic; this agrees 

 with the results of Lipman.^ It is of interest to note that there is 

 evidently a correlation between the production of NH3 of the organism 

 (as found by Lipman) and the rate of production of CO2 as shown 

 here. 



Fig. 5 shows the antagonism of salts. Thus, Curve A shows that 

 when five parts of NaCl and one part of CaCl2 (in the same molecular 

 concentrations) were added to the bacteria, the rate of respiration 

 remained normal, or as if no salt had been added. This was true 

 only when the proportions of 5 : 1 were used. When other proportions 

 were used the respiration decreased accordingly, and gave only a 

 fraction of the normal rate. This agrees with the results of Winslow 

 and Falk^ on the growth of Bacillus coli, but not with those of Lip- 

 man,^ on the production of NH3 by Bacillus subtilis, who found no 

 antagonism between NaCl and CaCl2. 



Curve B illustrates the effect of combinations of KCl and NaCl 

 upon the rate of respiration. There are two maxima in this curve; 

 one at 4 KCl to 6 NaCl, and the other at 6 KCl to 4 NaCl. The 

 former is the more nearly normal, although there is no combination 



