ANTAGONISM 



129 



We may now consider the effect of mixing two solu- 

 tions whicli are not equally toxic. Suppose solution A 0.1 

 M to be twice as toxic as solution B 0.1 M. The effect 

 of mixing these, if the effects were equally additive, would 

 be the same as mixing a solu- 

 tion of A 0.1 M with another 

 solution A just half as toxic, 

 or in other words, would be 

 the same as decreasing the 

 concentration of ^. In this 

 case the curve expressing 

 purely additive effects would 

 not be a straight line, but 

 would assume the form of a 

 curved line, convex to the 

 horizontal axis, similar to 

 FTTF in Fig. 51. This is evi- 

 dent^ from the curves given 

 by Magowan, showing growth 

 in toxic solutions of various a too 

 concentrations. ^ ^ 



It would be possible to Fiq. si— curves showing growth in mix- 



1 , . ii • 1 Ti" tures of unequally toxic solutions: the or- 



determine this additive curve dinates express growth; the abscissffi express 



, thecompositionof the mixtures as in Fig. 49; 



eXPenmentallv, and then to the dotted llne Vrif expresses the growth 



■•- •' ' which would occur if there were no antago- 



express antagonism quanti- ?re;^''fj'p{.:%frte'Upr'^s^ng''1nTease'd 



+n+l-0-Alv fnr PTnTTlTllp nt thp to^'^'ty .(opposite of antagonism); the 

 tdHVeiJ^ , lUl BAdlJipit;, <4L tlie quantitatiye expression of antagonism at the 



point P it would be expressed f™"* Pi<>vT^ tp. 



as UT -i- TP. But the labor would be much greater than 

 by the method of mixing equally toxic solutions. The 

 additive curve would be determined by growing plants, 

 not in mixtures of A with B, but in mixtures of A with 

 another solution of A having the same toxicity as B. Or 



'Magowan (1908). 

 9 



_75_ 

 25 



50 

 50 



25 

 75 



% 

 100 % 



