MATILDA M. BROOKS 531 



fact that in the experiments reported by Osterhout the highest pro- 

 portion of NaCl used was 500 to 1. Since this shows good antago- 

 nism, higher proportions were not tried, as the object of the experiment 

 was merely to demonstrate antagonism and not to ascertain the most 

 favorable mixture. 



Owing to the unusual results obtained with high dilutions of Na 

 taurocholate, it was thought advisable to procure Na taurocholate 

 from several different sources. The original product used was 

 Merck's. An additional sample was obtained from Eimer and 

 Amend, and some purified bile salts were kindly sent by Dr. Morgulis 

 and Dr. Hecht. Experiments made with all the above different sam- 

 ples were in remarkably good agreement, thus showing that the results 

 were not due to the impurities which might have been present in the 

 Na taurocholate. 



Experiments on recovery were made with a mixture of NaCl and 

 Na taurocholate (which produced a decrease in the rate of respiration) . 

 In the course of an hour, after removal of the bacteria from the mix- 

 ture to 0.75 per cent dextrose, the rate did not quite attain the normal. 



A few experiments with saponin were tried, inasmuch as it seemed 

 possible that the same mechanism might be responsible for the action 

 of Na taurocholate and for that of saponin. Eighteen concentrations 

 of saponin were used (ranging from 0.001 to 0.0000005 m), including 

 those which produce an increase in the rate of respiration in the case of 

 Na taurocholate. It was found that the concentrations which were 

 greater than 0.00005 m produced a progressive decrease in the rate, 

 while those which were less than 0.00005 m gave the normal rate of 

 respiration (100 per cent). None gave an increase in the rate of 

 respiration. 



Both saponin and Na taurocholate are exceedingly effective in 

 lowering surface tension but their effects on respiration are so differ- 

 ent as to indicate that surface tension does not play an important part 

 in this connection. This conclusion would not, however, be jus- 

 tified if it could be shown that saponin is unable to penetrate the cell. 

 The fact that in the highest concentrations employed^ there was some 



^ Higher concentrations were not employed on account of the foaming which 

 they produced. 



