A Point Scale for Measuring Mental Ability.

directions is obvious. It must depend on the gradient of chemical activity along the fiber, and the amount of increase of this activity at the point of stimulation. I believe the nerve impulse is a propagation of chemical change-the propagation being due to a restoration of an equilibrium disturbed by the increase of metabolism at the point of stimulus. This propagation is always toward the point where there is less chemical activity, as measured by carbon dioxide production.