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Walter Stiles 
nected with the cell wall, for in the present state of our knowledge it 
is not altogether certain that the cell walls of dead tissue are in the 
same state as those of the tissue before death. Even if the cellulose 
should be unaltered by the method of killing the tissue, other con¬ 
stituents of the cell wall and its general physical properties may be 
changed. 
But changes in the content and nature of the electrolytes in the 
protoplasm and cell sap are likely to contribute much more than 
changes in the cell wall to alterations of the conductivity. Anything, 
Such as diffusion, which brought about an increase in the quantity 
of free electrolytes in the protoplasm or cell sap, would raise the con¬ 
ductivity, and so would the breaking down of large complex mole¬ 
cules to smaller ones which undergo more ionisation or which give 
more mobile ions than the complex molecules from which they are 
derived. Such a change in the protoplasm might well involve an 
increase in its permeability, but the mere fact that its conductivity 
was higher, due to its higher content of ions or of more mobile ions, 
is not in itself to be interpreted as a proof of greater permeability. 
How difficult it is to interpret the results obtained by the con¬ 
ductivity method may be exemplified by reference to an experiment 
made by Osterhout (1918 b) in which Laminaria tissue was trans¬ 
ferred from artificial sea water containing sodium chloride to a 
similar solution having the same conductivity but in which lithium 
chloride was substituted for sodium chloride. This transference re¬ 
sulted in a fall in the resistance of the tissue, while on transferring 
the tissue back to the original medium the resistance rose. 
Osterhout states that these effects are clearly due to diffusion. 
He says that “the smaller molecules of LiCl diffuse in faster than 
NaCl can diffuse out, causing a temporary excess of salt, which lowers 
the resistance.” Now whatever the reason for the change in resist¬ 
ance the facts cannot be as Osterhout supposes, for the coefficient of 
diffusion of lithium chloride (in spite of its “smaller molecules”) is 
slightly lower and not higher than that of sodium chloride as shown 
for diffusion in water by Oholm (1905) and for diffusion in gels by 
the present writer. It is nevertheless encouraging that Osterhout 
acknowledges that factors other than permeability of the protoplasm 
can affect the electrical conductivity of tissue. 
In short, therefore, in the opinion of this writer, while changes in 
the conductivity of tissues may be correlated with similar changes in 
the permeability of the tissues, there appear to be so many other 
possible explanations of changes in electrical conductivity of tissue, 
