58 A CHEMICAL SIGN OF LIFE 
this region, assuming, of course, that the same strength 
of current when stimulating in or above the narcotized 
part is made use of. Since we have no evidence that the 
resistance of the surrounding sheath of the fiber and 
that of the conducting medium are the same, we cannot 
assume that in both experiments the same strength 
of stimulus was really applied to the conducting portion. 
The non-transmissibility of the inhibitory state is 
regarded as another distinction between excitation and 
conduction. We can abolish excitability at one point 
without making its neighboring region inexcitable. It 
is rather difficult to consider an analogy between depres- 
sion and excitation, but the fact is that even if we may 
not be able to make other than one point inexcitable 
by one depressing agent, it is doubtful whether we can 
produce local inexcitability without affecting the con- 
tiguous parts of the nerve. Waller has demonstrated, 
in the case of inhibition by heat, that the point of 
application of gentle heat became electropositive to the 
rest of the nerve instead of negative, as is the case in 
ordinary stimulation. According to him, heat does not 
stimulate the tissue, but depresses it. If this is the 
case, as he seems to have demonstrated in a variety of 
tissues, it indicates that although we cannot produce 
depression at points other than the point of application, 
yet certain conditions along the nerve must surely be 
altered through such an inhibition. In any event, we 
cannot consider non-conductivity of the inhibitory state 
as evidence that excitability and conductivity are 
entirely different processes. 
Let us now consider in detail the relation between 
excitation and conduction. 
