COMPARATIVE OBSERVATIONS ON MOTOR AND SENSORY FIBERS WITH SPECIAL REFERENCE TO REPETITIOUSNESS

Abstract

A study of the properties of motor and sensory fibers in the bullfrog (Rana catesbiana) with the electron oscillograph technique shows that as compared with motor fibers, presumably of the same sizes, the sensory fibers have the lower rheobase. the lower constant current threshold for repetition and exhibit the longer trains of repetition under a continuing constant current. They accommodate less and have the lower demarcation potential. They are the more responsive to currents of long duration and the less to brief currents, and perhaps conduct more slowly than the motor fibers. The results indicate that the sensory fibers have the "looser membrane." It has not been possible to substantiate a lag in the propagation of the sensory impulse through the ganglion, nor to demonstrate any greater effect of untoward conditions on conduction through the region of the ganglion in sensory as compared with motor fibers. No evidence has been found for a diversion of sensory action potentials into the ganglion cells. An instance is described of slow conduction in a fiber of high excitability.