ABSTRACT
The membrane properties of the longitudinal muscle fibre of the earthworm Pheretima communissima were investigated by intra- and extracellular stimulating methods.
The membrane potential was − 35·4 mV., and spontaneous discharges with overshoot (mean +18 mV.) and after-hyperpolarization (− 60 mV.) were recorded.
Tetrodotoxin (10−7 g./ml.) blocked nervous activity but did not influence the spontaneous discharges or the spikes elicited in the muscle fibre by intracellular stimulation.
The critical membrane potential required to elicit a spike was not constant, and the falling phase of the spikes was markedly dependent on the level of the membrane potential.
The chronaxie, measured from the intensity-duration relation to elicit a spike by intracellular stimulation, was 55 msec.
When nervous activity was excluded the propagation of excitation in longitudinal muscles was decremental.
