Fig. 7. Different effects of contractions by proximal and distal bundles of the flexor muscle on signalling by the lump receptor. (A) A single stimulus to the extensor muscle in an intact leg with the tibia fully flexed was followed by a burst of spikes from the lump receptor. (B) The same locust but with the flexor nerve (N5B2) cut in the middle of the femur, thereby preventing the distal muscle bundles from contracting. The contraction of proximal muscle bundles caused a burst of sensory spikes. (C,D) A second locust. (C) In the intact leg, sensory spikes followed the stimulus with the tibia fully flexed. (D) The flexor tendon was cut between the proximal and distal bundles of fibres so that the force developed by proximal fibres was not transmitted to the joint. Contraction of the distal muscle bundles was not followed by spikes from the lump receptor.