Permeability 139 
From these and other observations, as, for example, on the in¬ 
hibition of the toxic action of salts of copper and heavy metals by 
salts of the alkali and alkaline earth metals in regard to the germina¬ 
tion of fungus spores (J. F. Clark, 1901, 1902; Hawkins, 1913) there 
can be no doubt that antagonism is a very general phenomenon. 
But from these investigations, in which antagonism is determined 
by time taken to kill, amount of growth, or germinative capacity, 
there is no direct evidence that the antagonistic action of the sub¬ 
stances concerned is due to a mutual hindrance to the absorption of 
the two substances. The antagonism may result from reactions in 
the external solution, or in the cells thetnselves after the entrance 
of the substances. It is clear that the former can scarcely be a general 
explanation, as antagonism has been observed to take place between 
so many substances which do not react with one another. Evidence 
that the antagonism is indeed due, at any rate in some cases, to a 
mutual hindrance to the entrance of substances into the cell, has 
been forthcoming from other lines of experimentation. 
An observation of Benecke (1907), which appears to have been 
somewhat overlooked, affords more direct evidence of the effect of one 
electrolyte on hindering the entrance of another. As is well known, 
the entrance of an iron salt into the cells of a species of Spirogyra 
containing tannin, is rendered evident by the formation of a green 
or blue compound. Benecke observed that the entrance of ferrous 
sulphate into such cells is much delayed by the addition of a calcium 
salt to the solution of ferrous sulphate. This observation was con¬ 
firmed by Sziics (1910), who also found that the same result could 
be brought about by a number of salts, the antagonising action being 
a function of the valency of the kation, the higher the valency the 
greater the antagonising action. 
These results appear, at first sight, to be in complete discordance 
with those of Miss Williams (1918 b ) who found that cells which did 
not normally absorb ferric chloride would do so after treatment with 
solutions of various nitrates. It will be observed, however, that in 
Benecke’s experiment the two antagonising salts were present together 
in the same solution, whereas in Miss Williams’ experiments they 
were present singly and presented to the tissue one after the 
other. 
The non-entrance of the toxic substance in the reduction of toxic 
action by addition of some other substance to the toxic solution is 
also indicated by observations on the effect of barium salts on cells 
of Spirogyra. Osterhout (1916 e) showed that the chloroplasts of this 
