RESPONSE IN METALS 89 
From these experiments it will be seen how in one 
identical piece of wire the responsive current flows now 
in one direction and then 
in the other, in absolute 
conformity with theoretical 

A =e =| 

considerations. 
: Fic. 53.—METHOD oF 
Method of exaltation. —A ce are 
Soullmore striking corrobora- he contact Bis mademore excitable 
: by chemical stimulant (Na,WO,). 
tion of these results may, The current of response is towards 
however, be obtained by the a oh 
converse process of relative exaltation of the respon- 
siveness of one contact. This may be accomplished 
by touching one contact, say B, with a reagent which 
like Na,CO; exalts the electric excitability. On stimu- 
lation of the wire, the current of response is towards the 
more excitable B (fig. 53). 
I give four records (fig. 54) which will clearly 
exhibit the responses as obtained by the methods of 
relative depression or exaltation. In (a) B is touched 
with the excitant Na,CO;, a permanent current flows 
from A to B, response to stimulus is in the same direc- 
tion as the permanent current (positive variation). 
In (6) B is touched with a trace of the depressant 
oxalic acid, the permanent current is in the same 
direction as before, but the current of response is in 
the opposite direction (negative variation). In (c) B 
is touched with dilute KHO, the response is exhibited 
by a positive variation. In (d) B is touched with strong 
KHO, the response is now exhibited by a negative 
variation. The last two results, apparently anomalous, 
are due to the fact, which will be demonstrated later, 
