ANTAGONISM 



129 



We may now consider the effect of mixing two solu- 

 tions which 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 A. 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 

 VTW in Fig. 51. This is evi- 

 dent 7 from the curves given 

 by Magowan, showing growth 

 in toxic solutions of various A 100^ 

 concentrations. 



75 



% 



B 



25 



75 



100 % 



It WOUld be 



tO FIG. SI. Curves showing growth in mix- 



. -i j tures of unequally toxic solutions: the or- 



thlS additive CUrVe dmates express growth; the abscissae express 



the composition of the mixtures as in Fig. 49; 



experimentally, and then to th . e . dotted line VTW expresses the growth 



> ' which would occur if there were no antago- 



PYnrPQQ anf a D'nniQTn rmmrH- niem (additive effect); T't/TF, antagonism 



express diiidgo quaj curv ^. VSWt curve expressirig i ncre ased 



tfltivplv for AVarrmlp at tVlP toxici1 > v .(opposite of antagonism); the 

 UtllVtJlj , 1U1 tJJLeHllpic, dl -ic quantitative expression of antagonism at the 



point P it would be expressed point p is UT+TP - 



as UT -=- 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 



7 Magowan (1908). 

 9 



