ABSTRACT
The properties of a neuromuscular preparation of the mid-ventral pharyngeal retractor muscle of Cucumaria sykion (Lampert) have been previously described (Pople & Ewer, 1954). When excited by stimulation of the radial nerve, this muscle shows a double response consisting of a quick component, tentatively attributed to direct nervous paths through the motor complex of the muscle and a delayed component which possibly arises from secondary paths within the motor complex itself. This characteristic double response can be clearly seen in the contractions recorded in the upper trace of Fig. 2 of the present paper. The tension developed by this muscle is dependent upon the intensity of stimulation applied to the radial nerve. No evidence of frequency sensitive facilitation at the myo-neural junction was found.
This effect is not found for all preparations and may appear in only one or two muscles o f a five-muscle preparation. The cause of this variability is being investigated.
