1914] 



OSTERHOUT— ANTAGONISM CURVES 



369 



The figure shows in a diagrammatic way the effect of dilution 

 on the form of an antagonism curve. The lowest curve CDE shows 

 the effect on growth of various mixtures of two equally toxic solu- 

 tions io.i M+-S 0.12 M. The next curve shows the form of the 

 antagonism curve when all of these mixtures were diluted by the 



volume of water (A o.cx M+2J 



The 



next curve was pro- 

 duced by growing 

 plants in mixtures of 

 ^0.0025 M+50.03M. 

 The topmost curve was 

 obtained with mixtures 

 of A 0.001 M-\-B 

 0.0012 M. 



The pairs of pure 

 solutions were in each 

 case equally toxic, as is 

 shown by the fact that 

 the two ordinates at the 

 ends of each curve are 

 equal in height. 



It will be observed 



C 



E 



A 100 



50 



% 



B 







50 



100 % 



Fig. 2. — Diagram representing the composition 



that as the solutions of solutions (this serves as the base of the solid 



become more dilute the m °del shown in fig. 3) : the lowest line represents 

 , 1 , various mixtures of solutions of two salts, A and B; 



antagonism curve ^ be- the line EF represents the same m i xtU res diluted 



comes flatter, and it IS with equal volume of water; any line drawn parallel 

 evident that at Still to ^ w ^ express the same mixtures diluted to a 

 ff rP nt Pr rKl, t +;^c ;+ degree corresponding to the position of the line, the 



gicaier dilutions it . , . ^rwu *. *.u j-i *.• 



nearer it approaches to CD the greater the dilution; 

 must tend to become a on t he line CD all points represent distilled water. 



horizontal straight line. 



In order to give a complete description of the changes in the 

 antagonism curve as dilution increases, it is necessary to construct 

 a solid model. This might have as its base a triangular diagram as 

 described in a previous paper. 2 The apices of the triangle would 

 in that case represent A, B, and H 2 0. 



2 Box. Gaz. 58:178. 1914. 



