It is a chain of spontaneous activity in the four primary centers, establishing a circuit through the whole body.

But the positive poles are the lower centers.

And the brain has probably nothing at all to do with it.

Even the _desire_ to walk is not born in the brain, but in the primary nuclei.
The same with the use of the hands and arms.

It means the establishment of a pure circuit between the four centers, the two upper poles now being the positive, the lower the negative poles, and the hands the live end of the wire.