Neuromuscular Physiology of the Longitudinal Muscle of the Earthworm, Lumbricus Terrestris

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Abstract
An earthworm saline commonly used in previous investigations of earthworm neuromuscular physiology has been shown to be inappropriate for such studies because the ionic composition of the saline does not correspond to that of earthworm body fluids. Problems encountered when using this saline include: increased excitability of motor axons innervating the longitudinal muscle, a decrease in the amplitude of external electrical responses of the muscle, an increased susceptibility of longitudinal muscle fibres to injury spiking, and a decrease in resting potentials of longitudinal muscle fibres (to a mean of – 36·1 mV). Such problems have been overcome by the development of a new physiological saline whose composition closely corresponds to the ionic composition of earthworm body fluids. In the new saline responses of the nerve-muscle preparation remain stable for more than 1 h. Resting potentials of longitudinal muscle fibres are also stable with time, the mean resting potential being – 47·9 mV.