CHAPTER IV. 

 ANTAGONISM. 



When one toxic substance acts as an antidote to 

 another, we speak of this as antagonism. If the antagon- 

 istic substances are mixed in such proportions that tox* 

 icity disappears we have a physiologically balanced 

 solution as defined by Loeb. 1 



In seeking an accurate measure of antagonism the 

 writer made experiments on growth. It was found that 

 both NaCl and CaCl 2 are toxic to plants, as shown by the 

 fact that in solutions of these substances there is less 

 growth than in distilled water. 2 In a series of experi- 

 ments on wheat, it was found that the growth of roots 

 in NaCl 0.12 M was practically the same as in CaCL 0.164 

 M. These solutions were therefore regarded as 

 equally toxic. 



On mixing equally toxic salt solutions, we may 

 encounter one of the following conditions : 3 



1. The toxicity is unaltered, that is, the toxic action 

 of the two salts is additive. Each salt produces its own 

 toxic effect precisely as though the other were not present. 

 This is expressed by the horizontal dotted line LJM in 

 Pig. 49. 



It is evident that we cannot get increased growth by 

 mixing two such solutions unless the salts have an antag- 

 onistic action. If we mix equal volumes of A 0.1 M and 



1 Cf. Loeb, J. (1906, B). For the literature of antagonism see Loeb 

 (1909), Robertson (1910), Hober (1914). 



3 This statement does not apply to very dilute solutions. 

 8 (7/. Osterhout (1914, B, C; 1915, F). 



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