The Only New Thing in the Hypothesis 299 
counts for the fact that a small stimulus as cause may 
often result in an extraordinarily great reaction, just as 
a grain of gunpowder kindled by a small spark may 
provoke the explosion of a great mass.” 218 
We have opened this parenthesis on nuclear somatiza- 
tion and cited these passages from the two investigators 
in order to set in clear relief the fact that in the definition 
given above of the specific potential elements, both the 
conception of accumulators of nervous energy in tension, 
and that of accumulators of a specific nervous energy con- 
stituting their special irritability, are ordinary conceptions 
very generally employed which are expressed here in 
words at most only a little different from the ordinary. 
The only new thing which the above definition includes 
is the hypothesis that the substance which is thus capable 
of giving as a discharge a given nervous current was pro- 
duced and deposited only by a nervous current of the 
same specificity, but in the inverse direction, and could 
have been produced and deposited only by such a current. 
But in this hypothesis, quite simple as it is, lies every- 
thing; for it is just it which alone can explain completely 
the fundamental law of the reversibility of the relation 
between action and reaction, between stimulus and im- 
pression, which governs all organic life. The inheritance 
of acquired characters, the psycho-mnemonic phenomenon 
proper, the process of specialization and somatization of 
the cells in consequence of which they react in their 
habitual manner to accidental stimuli unusual to them, 
even the vital phenomenon itself in all its generality, all 
of these, as we have seen and shall see, are only so many 
218Oscar Hertwig: Die Zelle und die Gewebe I, P. 77. 
