Walter Stiles 
224 
same rule (Kahho, 1921 c). Kahho explains all these relations on 
the view that toxic action depends on power of penetration, while 
power of penetration depends in inverse fashion on capacity for 
coagulating certain of the cell colloids, probably the lipoid con¬ 
stituents of the protoplasm. Thus the reason why a calcium salt 
reduces the toxicity of a sodium salt is that the calcium coagulates 
the lipoid constituents of the limiting layer of the protoplasm, which 
according to Hansteen-Cranner (1919, 1922) penetrates into the 
interstices of the cellulose-pectin (“ cellulose-hemicellulose ”) colloidal 
network of the cell wall. This coagulation of the lipoid constituents 
renders the outer layers of the protoplasm less permeable to the salts 
in the external solution so that the entrance of these salts with their 
consequent toxic action is prevented and the coagulation of the 
proteins of the protoplasm is thereby prevented. 
This theory is attractive and Kahho marshals his own experi¬ 
mental data well in its support and adduces a number of observations 
by other workers as evidence on behalf of his theory. It must never¬ 
theless be admitted by an unprejudiced critic that the experimental 
basis of the theory is still rather frail, the essential facts, namely, 
those relating to the actual penetration of different salts, having 
been obtained by the tissue extension method of Lundeg&rdh, the 
vahdity of which, for reasons advanced in an earlier chapter, is open 
to a certain degree of doubt, and which should certainly be confirmed 
by means of other methods of determining salt absorption. Consider¬ 
ably more work on the location and properties of the cell colloids in 
the actual species used would also appear desirable. 
(To be continued) 
