A computer model of the musculoskeletal system of the lobster gastric mill was constructed in order to provide a behavioral in(cid:173) terpretation of the rhythmic patterns obtained from isolated stom(cid:173) atogastric ganglion. The model was based on Hill's muscle model and quasi-static approximation of the skeletal dynamics and could simulate the change of chewing patterns by the effect of neuromod(cid:173) ulators. The crustacean stomatogastric ganglion (STG) is a circuit of 30 neurons that con(cid:173) trols rhythmic movement of the foregut. It is one of the best elucidated neural circuits. All the neurons and the synaptic connections between them are identi(cid:173) fied and the effects of neuromodulators on the oscillation patterns and neuronal characteristics have been extensively studied (Selverston and Moulins 1987, H arris(cid:173) Warrick et al. 1992).