350 Stiles and J0rgensen.—Studies in Permeability. I. 
In this connexion it is of importance to compare the researches on 
antagonism of those workers who have attempted to obtain quantitative 
data. Although qualitatively antagonism is generally regarded as the 
hindrance of the entrance into the plant, or through the plasma membrane, 
of one ion by another ion of the same sign, yet when quantitative results 
are attempted it is clear that different workers have been measuring different 
things. Thus Osterhout ( 18 , 19 , 20) attempts to measure antagonism 
between two metallic ions by finding what strength of solution of salts 
of the two metals are equally toxic, and then mixing these two solutions 
in various proportions. If then each ion of either metal was as toxic in the 
mixed solution as in the pure solution, it should follow that all such mixed 
solutions would be equally toxic. It is found in certain cases that as 
a matter of fact this is not so, and that the mixed solutions allow of better 
growth than the pure solutions. The increase of growth, as compared with 
the growth in the pure solution, is regarded by Osterhout as a measure of 
the antagonism, which is greatest for one particular ratio of the antagonizing 
ions, and becomes less as either of the two ions becomes more concentrated 
at the expense of the other. 
On the other hand, Sziics and some other writers have kept the 
quantity of one ion (the poisonous ion) constant, and have added various 
quantities of the other (the depoisoning ion). If the latter is much less 
toxic than the former, increase in the depoisoning ion reduces the toxicity 
of the poisonous one. This action is explained by Sziics as due to the 
hindrance of the entrance of one ion owing to the presence of the other. 
When only one ion is present the whole of the absorbing part of the 
plasma membrane is available for its passage, but when another ion is 
present a certain proportion of the absorbing part of the membrane will 
be used by the second ion. Hence, if this is a relatively harmless ion in 
comparison with the first, the more of the second ion that is present, the 
less of the more harmful ion will go in, so that within limits the more of 
the second ion that is added the greater the depoisoning. Above a certain 
concentration, however, the depoisoning ion will itself exert an injurious 
action. 
In this way Sziics explains the antagonistic action of aluminium and 
copper. Now it will be observed at once that in this way of regarding 
antagonism, no antagonism is to be expected in the mixtures employed by 
Osterhout. The antagonism between copper and aluminium on the one 
hand, and that between ‘ nutrient ’ metals on the other, seem therefore to 
be different phenomena. 
It thus seems that although Loeb’s idea of antagonism was a great 
advance, it appears to have produced a mechanical way of regarding as one 
definite phenomenon all the observed cases, whereas it may be due to 
different underlying causes in different instances (cf. Hawkins (6)). 
