Fig. 52.—Response by Method of Depression (Without Block)
When the wire is stimulated as a whole the current of response is towards the more excitable.
In (a) A is a normal contact, B has been depressed by oxalic acid; current of response is towards the more excitable A.
In (b) the same wire is used, only A is depressed by oxalic acid and a normal contact is made at a fresh point B′, a little to the left of B in (a). Current of response is now from A towards the more excitable B′.
A corroborative reversal experiment may next be made on the same piece of wire. The normal contact, through water or salt solution, is now made at B′, a little to the left of B. The excitability of A is now depressed by oxalic acid. On stimulation of the whole wire, the current of response will now be found to flow in an opposite direction—i.e. from A to B′—but still from the relatively less to the relatively more excitable ([fig. 52], b).
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 considerations.
