succeeds in maintaining the greater part of the occupation energy in a dormant state and in using but a small portion for the purposes of displacement. The mechanism of these processes is entirely unknown to me; any one who wishes to follow up these ideas must try to find the physical analogies and prepare the way for a demonstration of the process of motion in the stimulation of the neuron.

I merely hold to the idea that the activity of the first ?-system is directed to the free outflow of the quantities of excitement, and that the second system brings about an inhibition of this outflow through the energies emanating from it, i.e. it produces a transformation into dormant energy, probably by raising the level. I therefore assume that under the control of the second system as compared with the first, the course of the