208 
Walter Stiles 
These various assumptions are unjustified by the facts. With 
regard to the first assumption, equilibrium in the intake of copper 
sulphate was shown by Szucs to come about very slowly. With regard 
to the second assumption, it is not true that small quantities have the 
same effect as larger ones if they are given the necessary time to act, 
for the intake of small quantities of a poison may not lead to death. 
That this is not due to the washing out of the poison into the sur¬ 
roundings is shown by the fact that it takes place with heavy metals 
which are supposed to form irreversible compounds with the cell 
proteins, and that if plants are grown with their roots in a poisonous 
solution and removed from it before the lapse of a definite critical 
time they survive. Finally, with regard to the third assumption, 
Szucs found that with very poisonous substances death may occur 
before the equilibrium condition is reached. 
For these reasons Szucs held that Ostwald’s theory could not 
be maintained in its original form. Szucs himself appeared to incline 
to the opinion of Morawicz (1910) that the same quantity of material 
must be absorbed to bring about death. Szucs himself found the 
time required for seedlings of Cucurbita Pepo to absorb enough 
copper sulphate to kill them, by maintaining their roots in the copper 
sulphate solutions for definite times and then testing their vitality 
by examining their power to react to the stimuli of light and 
gravity. He then found that where t is the time required for the 
seedlings to take up enough copper sulphate to inhibit the geotropic 
reaction, 
7 = kC*. 
k, C and p having the signification previously assigned to them. 
But these considerations on the relation between the concen¬ 
tration of toxic substances and time taken to kill, do not help us very 
much in determining the influence of concentration in bringing about 
a change in permeability. They have, however, this bearing on our 
subject, that, according to the view involved in Wolfgang Ostwald’s 
theory, a substance that produces irreversible changes in permeability 
leading to death, would do so at once, whereas according to the view 
of Szucs the action of the toxic substance might only become irrever¬ 
sible after a definite critical period of immersion, varying in length 
with the concentration according to the equation cited above. 
It is at least possible that all changes resulting in increased per¬ 
meability of the cell are reversible if the condition producing the 
change is not allowed to act for more than a certain time. 
