Rate of COg production 



ioo7o 



50 



0-- 





 10 



10 



occ. 



Fig. 3. Curves showing antagonism in the effect of salts on the respiration of 

 Bacillus subtilis (expressed as per cent of the normal). Curve A, antagonism 

 between 0.8 m NaCl (left), and 0.8 M MgCl2 (right); Curve B, antagonism 

 between 0.8 M CaCl2 (left) and 0.8 M MgCl2 (right). The ordinates represent 

 rate of respiration (expressed as per cent of the normal); the abscissae repre- 

 sent molecular proportions of the salts used. Thus, in Curve A, the ordinate 

 at the extreme left represents the rate in 0.8 m NaCl, while the ordinate at the 

 extreme right represents the rate in 0.8 M MgCl2. The ordinate in the middle 

 represents the rate in 50 parts of 0.8 M NaCl, and 50 parts of 0.8 m MgCl2. 

 In Curve B the ordinate at the extreme left represents the rate in 0.8 m CaCl2, 

 while the ordinate at the extreme right represents the rate in 0.8 M MgCl2. 

 The normal rate (which is taken as 100 per cent) represents a change in pH from 

 7.78 to 7.60 in about 30 seconds, varying according to the number of bacteria 

 used. Curve A, average of three experiments; Curve B, average of three experi- 

 ments. Probable error less than 3 per cent of the mean. 



335 



