ANTAGONISM 163 



writer, it turned out that magnesium was able to decrease 

 conductivity, though its effect was much inferior to that 

 of calcium. The antagonistic relations for Laminaria 

 were then investigated, and it was found that MgCl 2 was 

 able to antagonize NaCl, though its antagonistic action 

 was much less than that of CaCl 2 . 



This unexpected and striking result strengthened the 

 writer's confidence in the hypothesis and led to further 

 investigations. One of these which was of special interest 

 related to acids. For a number of reasons it was sup- 

 posed that acid would not cause a decrease in permeabil- 

 ity. But investigation showed that such a decrease actu- 

 ally occurred in the presence of HC1 and it was then a 

 simple matter to predict that antagonism would be found 

 between NaCl and HC1. This turned out to be the case, 

 the amount of antagonism corresponding to the amount 

 of decrease of conductivity. 



These results are also of interest in view of the fact 

 that Loeb 29 has shown that salts are antagonized by acids 

 and has pointed out that this has a special significance 

 for the theory of permeability, since it indicates that the 

 permeability of the plasma membrane (for water and 

 substances soluble in water) depends on the presence 

 of protein rather than of lipoid substances. The investi- 

 gations of the writer show that similar (though less 

 striking) antagonism occurs in plants. This affords 

 evidence of the protein character of the plasma mem- 

 brane in plants and is in harmony with the fact that (as 

 the writer has shown) various ions pass through the 

 plasma membrane of plants, 30 which would not be 

 expected if it were composed of lipoid. 



^Loeb, J. (1899; A, B; 1912, A, B; 1917): Loeb and Wasteneys 

 (1911, B; 1912). 



30 Cf. Osterhout (1912, A, B; 1913, B). 



