532 STUDIES ON RESPIRATION. XV 



depression^ of the rate of respiration indicates that saponin penetrates 

 to some extent. 



It is interesting to observe that the results obtained with Bacillus 

 suhtilis resemble those obtained by Osterhout in measuring the elec- 

 trical conductivity of Laminaria, since in both cases the effect of 

 saponin^ is very much less than that of Na taurocholate. 



SUMMARY. 



1. The addition of Na taurocholate produces an increase in the 

 rate of respiration at a concentration of 0.0000125 m, and a decrease 

 at 0.001 M and in higher concentrations. 



2. NaCl is antagonized by Na taurocholate, the most favorable 

 proportion being 14,375 parts of NaCl to 1 part of Na taurocholate 

 (molecular proportions) . 



3. Solutions of saponin, at concentrations from 0.00005 m to 0.001 m, 

 decrease the rate of respiration: lower concentrations produce no 

 effect. 



^ The depression was not due to the buffer action of the saponin. This was 

 shown by comparing the change in pH produced in the saponin solution and 

 in distilled water when a solution of carbonic acid was added to each. 



^ Unpublished results of experiments on Laminaria. 



