507 
Protoplasm to some Reagents. 
possible, yet, without experimental data to support it, it seems preferable to 
regard the critical toxic tension value set by Czapek as one not proven to 
exist in the sense which Czapek intended it. 
The theory of Czapek was early criticized by Vernon ( 25 ), and later 
received drastic criticism at the hands of Stiles and j0rgensen (22). These 
workers repeated the experiments of Czapek, employing the electrical con¬ 
ductivity method of Kohlrausch for determining the exosmosis of electro¬ 
lytes. As a result of their experiments they conclude that, ‘ not only is 
the theory founded by Czapek upon his experimental results untenable, 
but . . . the facts on which he bases his theory are merely illustrations of 
experimentation due partly to the crudity of the method employed, and 
partly to a selection and arbitrary arrangement of experiments ’ (22, p. 50). 
That Czapek’s theory is not universally applicable is true. One need 
merely consider the ‘oligodynamic * ( 9 ) action of copper water (the term is 
Nagelds, and refers to the extremely high toxicity of water in which there is 
a slight trace of copper). The action of copper water (water in which several 
copper coins had remained overnight) on Elodea leaves was found by the 
writer (21), in its effect on permeability and protoplasmic streaming, to be 
similar to and as pronounced as that of saponin. The same is true of a weak 
(1 percent.) solution of strontium chloride. Yet both of these highly toxic 
solutions possess a surface-tension value which differs exceedingly little 
from that of pure water. 
Czapek himself found that some reagents do not fit in with his theory, 
and he assumed in these cases that a ‘ special toxic action ’ takes place. 
Such an assumption is destructive to his theory in so far as its universal 
applicability is concerned. However, in reply to Vernon, Czapek made one 
statement which stands in substantial support of his hypothesis. He 
( 7 , p. 111) stated that his theory must collapse only when there has been 
found one substance which in spite of a surface-tension value below 0-685 
not deadly. 
Czapek’s theory fails utterly as a complete explanation of all per¬ 
meability changes due to the poisonous action of toxic substances. But the 
entire sweeping aside of the theory is not, in my opinion, justifiable ; that 
is, we cannot completely ignore the possibility of alterations in surface 
tension being a factor, and possibly a very prominent factor, in permeability 
changes. 
It is most remarkable that substances which differ chemically so 
widely as do ethyl alcohol and saponin (and strontium chloride and copper 
oxide) should all cause the same pronounced change in the physiological 
condition of protoplasm. One hesitates to believe that any one theory will 
explain the reaction of protoplasm to all these reagents even though the end 
result, an increase in permeability and a stimulation to streaming, is the 
same in each case. 
