SOME CONDITIONS AFFECTING INTENSITY AND DURATION THRESHOLDS IN MOTOR NERVE, WITH REFERENCE TO CHRONAXIE OF SUBORDINATION

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Abstract
In expts. on decerebrate cats and frogs a decrease in rheobase and increase in chronaxies, such as that described by M. Lapicque upon release of peripheral nerve from central control, was found to be correlated only with proximity of the nerve section to the electrodes. On the hypothesis that lowered rheobase was due to partial stimulation by injury current, duration of minimal exciting currents was measured at fixed increments of voltage above the rheobase. The principal effects of injury were decrease in rheobase, a slight decrease in time parameter, and a slight change in a third parameter. Chronaxie is an inaccurate measure of excitation time under conditions of changing rheobase. The changes in rheobase and chronaxie when the nerve was sectioned outside the effective range of the injury were insignificant; the voltage increment method usually revealed no change in time factor. Expts. on cutting the spinal cord, on anesthesia and on proprioceptive stimulation failed to support the theory of "subordination." Evidence and arguments previously advanced in support of this theory revealed inconsistencies.

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