Duration of the Quaternary and Its Subdivisions.

which underlie the restoration of nerve fibers by the anodal current (cf. ref. 6, chap. XIII). A certain periodicity of the variations of threshold appears in curve V (Fig. 5), the period corresponding approximately to internodal lengths. The question, however, must be left open whether such a periodicity was coincidental or was due to the fact that with the nerve fiber in a certain state the anesthetic acts more strongly upon certain parts of the internodes than upon other parts. Summary.-Evidence has been presented to show that all points of the internodes of peripheral myelinated fibers produce action potentials in response to applied cathodal currents, the stimulation threshold being practically uniform throughout each internode. Anesthetics act upon all points of the internodes. Model experiments have shown that the nodes of Ranvier can have only a negligible effect on the electrotonic flow of action currents, or applied currents, throughout the myelinated internodes.