Permeability 207 
It has previously been mentioned that the electrical conductivity 
of tissue increases when acted upon by a toxic substance, the rate 
of increase giving a rough measure of the toxicity (Osterhout, 1912 a; 
Raber, 1920 a ). Osterhout’s elaborate theory of antagonism de¬ 
scribed in the last chapter is easily extended so as to explain the 
changes in electrical conductivity of tissue acted upon by a toxic 
substance (Osterhout, 1917 e). 
The relation between concentration and toxicity was investigated 
by Wolfgang Ostwald (1907) in the case of a freshwater animal, 
Gammarus , this worker coming to the conclusion that the life-time t 
of the animal in a solution of concentration C is given by the equation 
i=.AC* 
Z 
where k and p are constants. 
The similarity of this equation to the adsorption equation led 
Ostwald to regard ^ as proportional to the quantity of toxic substance 
adsorbed. The law has been shown to hold by Weevers (1912) for 
the toxic action of chloroform vapour on cells of the root of the red 
beet, the exosmosis of the red pigment being taken as an indication 
of the death of the cells. The same worker found (1914) that this re¬ 
lation only held within narrow limits in the case of the poisoning of the 
same cells with solutions of quinine hydrochloride and chloral hydrate. 
With more dilute solutions the cells live longer than the time in¬ 
dicated by Wolfgang Ostwald’s equation. A similar divergence was 
observed by Sziics (1912) in his experiments on the time required 
for seedlings of Cucurbita Pepo to absorb enough copper sulphate 
to kill them, and by Nothmann-Zuckerkandl (1912) in experi¬ 
ments on the action of alcohol on protoplasmic streaming in 
V allisneria. 
Several arguments against Ostwald’s conclusion have been put 
forward by Sziics, who showed that the former writer’s view that the 
time taken to kill is inversely proportional to the quantity of poison 
adsorbed involves several assumptions. It assumes in the first place 
that equilibrium between the quantity adsorbed and the outer medium 
appears instantaneously, for otherwise the life-time will be increased. 
In the second place it is assumed that small quantities have the same 
effect ultimately as larger ones, but require more time for the effect 
to be observed. Thirdly, it is assumed, since the adsorption equation 
only refers to an equilibrium condition, that the toxic effect is only 
produced when the equilibrium is reached. 
