Fig. 1. Schematic illustrating the neural innervation of the dactyl opener and closer muscles of the propus and the stretcher muscle of the carpus of the lobster walking leg. Muscles are indicated by boxes; within the boxes are abbreviations for the names of the innervating motoneurons. Lines illustrate the innervation paths of the axons of each of the motoneurons. The opener muscle receives innervation from the common inhibitor (CI), the opener excitor (OE) and the specific opener inhibitor (OI). Placement of suction electrodes for stimulation of the axons of these motoneurons is illustrated by numbered arrows. (1) The axon of OE is stimulated by an electrode placed on the nerve running between the stretcher and opener muscle; this nerve contains the axon of OE (black line) as well as CI (see Results). (2) The axon of OI is stimulated via its axon (heavy black line) in the main nerve trunk in the carpus. (3) The axon of CI (broken lines) is stimulated by an electrode placed on a nerve branch that stretches between the opener and closer muscles. The innervation of the closer muscle and the stretcher muscle is also shown: the closer is innervated by fast and slow excitatory axons (FCE and SCE) as well as by CI, while the stretcher is innervated by CI as well as the stretcher excitor (SE). The stretcher excitor SE is another name for the opener excitor OE; both muscles are innervated by the same excitatory axon.