The Giant Fibre Reflex of the Earthworm, <i>Lumbricus Terrestris</i> L.

Abstract

ABSTRACT A nerve-muscle preparation including the longitudinal musculature and the giant fibres in the nerve cord of the earthworm is described. Direct stimulation of the nerve cord with single shocks of increasing intensity results in two types of response: (a) a low threshold, very small twitch, resulting from a single impulse in the median giant fibre, and (b) a higher threshold, slightly larger twitch, resulting from single impulses in the median and lateral giant fibres. Both responses are highly susceptible to fatigue. Stimulation of the body surface evokes a much more powerful contraction which is associated with a burst of impulses in the giant fibre. The strength of the contraction depends upon the number of impulses in the burst and this in turn upon the intensity and duration of the stimulus.