Permeability 147 
lene blue and neutral red suggest that the phenomenon cannot be 
so simply explained. 
Osterhout (1916 b, d, 1917 c) has formulated what he calls a 
“dynamical theory of antagonism” based ultimately on the assump¬ 
tion that “an accurate measure of antagonism is furnished by the 
electrical resistance of living tissues.” It is found that substances 
are of two kinds, those like sodium chloride, which bring about a fall 
in the electrical resistance of the thallus of Laminaria Agardhii and 
other plants, and those which, like calcium chloride, bring about an 
increase in electrical resistance followed very shortly (often within 
15 minutes) by a decrease in resistance, which proceeds, as in the case 
of the first group of substances, to a maximum when the tissue 
is dead. 
Osterhout supposes that two processes are involved, one pro¬ 
ducing a fall in resistance, the other a rise. He assumes that these 
two processes can be represented by the simple scheme 
where the substance A breaks down to form an intermediate sub¬ 
stance M which itself breaks down to form B. It is further assumed 
that the resistance of the protoplasm is due to the intermediate 
substance M (“a substance at the surface of the cell which offers 
resistance to the passage of ions” (Osterhout, 1917 c )), and that the 
resistance of the tissue is proportional to the quantity of M + a 
constant equal to the resistance of the tissue when dead. 
It is assumed that in Laminaria under normal conditions in sea 
water, the quantity of each of these substances remains constant. 
On transferring the mixture to a solution of sodium chloride or 
calcium chloride, or a mixture of the two, it is further assumed that 
the velocity constants of the two reactions A -> M and M -> B are 
altered. Then, if the reaction A -> M is more rapid than the reaction 
M -> B, M will accumulate and the resistance will be raised until the 
supply of A becomes exhausted when M will form more and more 
slowly, so that ultimately it will decompose faster than it is formed, 
when the resistance will fall. 
Values can be selected for the velocity constants of the two 
reactions so that on the assumptions already made curves between 
time and quantity of the substance M present can be constructed 
which agree with the curves of resistance of Laminaria in sodium 
chloride, calcium chloride or any mixture of the two salts. It 
is then found that as the quantity of calcium chloride in the 
solutions increases, the velocity constants of both the actions 
10—2 
