MATILDA M. BROOKS 15 



after centrifugating them to see whether or not the mechanical manip- 

 ulation was responsible for the normal rate. The rate, however, 

 showed no recovery under these conditions. 



In order to find out whether the pH value of the liquid containing 

 the bacteria changed when the salts were added, thereby influencing 

 the rate of respiration, an indicator was added to this Hquid in the 

 apparatus and the pH value was observed to remain so nearly constant 

 that the change in the rate of respiration could not be attributed 

 to changes in alkalinity of the medium in which the bacteria were 

 placed. 



SUMMARY. 



1. In relatively low concentrations of NaCl, KCl, and CaCU the 

 rate of respiration of Bacillus suhtilis remains fairly constant for 

 a period of several hours, while in the higher concentrations, there 

 is a gradual decrease in the rate. 



2. NaCl and KCl increase the rate of respiration of Bacillus suhtilis 

 somewhat at concentrations of 0.15 m and 0.2 m respectively; in 

 sufficiently high concentrations they decrease the rate. CaCl2 in- 

 creases the rate of respiration of Bacillus suhtilis at a concentration 

 of 0.05 m and decrease's the rate at somewhat higher concentrations. 



3. The effects of salts upon respiration show a well marked antag- 

 onism between NaCl and CaCl2, and between KCl and CaCl2. The 

 antagonism between NaCl and KCl is slight and the antagonism 

 curve shows two maxima. 



