The electrotonic potential appearing in a stimulated dorsal root is found to be the resultant of two independent systems of current of different origin.

One component, labelled DRα, is non-occluding.

The other component, labelled DRß, occludes strongly and has the characteristics of the potential which appears in a neighboring unstimulated rootlet (DRIV-V).

Because DRα does not occlude, its origin is assigned to the primary afferent neuron. The result of a general examination of its origin leads to the additional conclusion that it must arise from a physiological spatial gradient in the post-spike recovery cycle of membrane potential along the afferent neuron.

The specific locus of this gradient within the primary neuron is the subject of the succeeding paper (16).

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