255 
Absorption of Salts by Plants: 
calcium. This causes a structural disturbance of account of 
which the protein substances cease to be active and death ensues. 
It will be observed that this theory will only explain the need for a 
balance between calcium and magnesium ; it is not a general theory 
of antagonism. In the case of calcium and magnesium the seat 
of the antagonistic action on this theory is inside the cell in the 
nucleus and plastids; in this respect, as we shall see later, Loew’s 
theory differs fundamentally from the opinions arrived at by some 
more recent workers. 
Work dealing directly with Antagonism. 
The modern conception of antagonism is due to Loeb who 
commenced publishing on this subject in 1901 ; a general account 
of his work appears in his “ Dynamics of Living Matter” (14). He 
worked on the development of Fundulns eggs in various solutions. 
He found that these eggs are unable to form an embryo if put 
immediately after fertilization into a solution of pure NaCl of the 
same concentration as that of this salt in sea-water. This toxicity 
is reduced if a small definite quantity of the salt of a bivalent metal 
is added to the NaCl solution. The salt of any bivalent metal is 
able to produce this effect except those of very poisonous metals 
such as mercury; even such poisonous salts as those of lead are 
able to produce this result. That this effect is due to the kation 
was shown by using different salts of the same metals. Trivalent 
kations were also capable of rendering the toxicity of salts of 
univalent metals less harmful; but a tetravalent kation, thorium, 
was found to have only a slight depoisoning effect. The reverse is 
also true, for monovalent ions were found capable of reducing the 
toxicity of salts of zinc. A slight antagonism was also observed 
between two divalent kations, such as Sr and Mg. 
The relative quantity of the depoisoning ion that has to be 
added varies with the concentration of the toxic solution. Thus 
M 
with Fundulns a concentration of NaCl is harmless; with a 
concentration of § m NaCl one bivalent ion is required to render 
1000 Na ions harmless. Between these two concentrations of 
NaCl the relative quality of bivalent ion required is less, while it is 
impossible to render harmless a solution of NaCl above a certain 
concentration. 
It is interesting that these antagonistic effects only hold for 
the eggs and not for the larvae of Fundulns. Loeb, therefore, 
concludes that the antagonistic effects only appear so long as the 
