EFFECT OF ACIDS ON TYPHOID AND COLON BACILLI 277 



TABLE 13. 



DISINFECTANT ACTION OF SULPHURIC ACID ON B. typhi IN i PER CENT PEPTONE SOLUTION. 



TABLE 14. 



COMPARATIVE TOXICITY OF MINERAL ACIDS IN DISTILLED WATER AND i PER CENT PEPTONE SOLUTION. 

 (Parts per 1,000,000 of dissociated hydrogen.) 



It is evident that in some way the peptone exerts a strong influence 

 in counteracting the toxic effect of the acids. It at first occurred to 

 us that this might be due simply to the fact that peptone solution 

 furnished a more favorable medium for the bacteria, and thus enabled 

 them to resist unfavorable conditions. Such an effect would, how- 

 ever, hardly be expected in so short a period as 40 minutes ; and this 

 explanation fails to account for the fact that the toxicity of the hydro- 

 chloric acid is much more diminished than that of the sulphuric acid. 

 Reference to Tables 15-17, which show the results obtained with the 

 organic acids, makes it still clearer that a specific chemical action is 

 involved. 



Evidently with the organic acids disinfectant power is much 

 less affected by the presence of peptone. With B. coli acetic acid 

 produces a 100 per cent reduction when in a strength of 0.0935 



