MANIFESTATIONS OF SEGMENTATION IN MYELINATED AXONS

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Abstract
If, while recording with the cathode ray oscillograph the conducted action potential of the most irritable fiber in a sciatic-phalangeal nerve of Rana pipiens, the region led from increasingly anodally polarized, a series of waves delimited by notches can be made to develop on the spike and these waves can be serially blocked. This notching develops in such a way as to indicate that the phenomenon has a normal foundation. Comparable results are given by cathodal polarization and by Ringer''s solution containing an excess of Ca or of K. Ca block can be reversed by anodal polarization. The waves are believed to represent the responses of the segments located within the range of effective extension of the fiber''s potential to the leads. Among others the possibility is considered that segments act as units. If so, the normal segment potentials would have rising and falling times of not over 0.15 and 0.45 milliseconds, respectively. The duration of the conducted spike of any axon as recorded would then be the duration of its segment response plus the time for conduction of the impulse the distance of the appreciable action potential spread, ca. 4 mm.