The Initiation of Nerve Impulses by Mesenteric Pacinian Corpuscles

A preparation of a single Pacinian corpuscle in the cat’s mesentery has been used to study the initiation of nerve impulses in sensory endings. The minimum movement of a mechanical stimulator required to excite a single corpuscle has been found to be 0⋅5μ in 100 μsec. It has been difficult to produce repetitive discharges with rectangular pulses of long duration, either mechanical or of constant current. The latency between a mechanical stimulus and the initiation of an impulse has a value around 1⋅5 msec, for threshold stimuli, and this decreases to a minimum value around 0⋅5 msec, as the stimulus is increased; it is altered only slightly, if at all, by changes in the duration of the maintained displacement of the mechanical stimulator. Subthreshold mechanical stimuli have been shown to facilitate stimulation by electrical test shocks. The return of excitability at the ending is independent of the nature of the conditioning stimulus and varies but little with the nature of the test shock. The value of the latency at threshold is unaffected by the relatively refractory state. The relations of these results to various hypotheses are discussed, and it is suggested that these results can all be accounted for in terms of the known properties of axons.