466 



JAMES M. SHERMAN AND GEORGE E. HOLM 



tioiis, and the time for growth in each series, are shown in' table 1 . 

 This table shows a decided accelerating effect upon growth with 

 added NaCl in low concentrations. Although there was little 

 difference between the effects of 0.10, 0.20 and 0.30m NaCl 

 media upon growth, there seems to be an optimum effect at 

 about 0.20m. The optimum H-ion concentration for growth 

 either in controls or in pepton containing NaCl at various con- 

 centrations seems to be about the same, approximately pH 7.8. 

 At optimum salt concentrations there is very little difference in 

 the rate of growth over a wide range of H-ion concentration, 



TABLE 1 

 The rale of growth of Bad. colt in various concenlrations of NaCl in 1 per cent pep- 

 tone and at various H-ion concentrations 



varying from 5.3 to 8.3 on the pH scale, while in the pepton 

 solution alone the range is somewhat narrower. Beyond the 

 range for optimum growth there seems to be a decided retarda- 

 tion for each small change of H-ion concentration. These 

 results are brought out more clearly in figure 1 which shows a 

 pronounced widening of the limiting pH values for growth with 

 added NaCl, especially in optimum salt concentrations, and a 

 retardation of growth for each small change in pH near the 

 luniting values. 



In order to ascertain if there was actually a shifting of the 

 limits of growth, or merely a widening of the optimum range 

 for growth, the effect of NaCl was tried at pH values representing 

 the approximate limit of growth in the acid region. At a pH of 

 4.8 it was found that only rarely would Bact. coU grow in 1 per 

 cent pepton at 37°C., but that it did grow quite readily in the 



