Statocyst-Induced Eye Movements in the Crab Scylla Serrata*

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Abstract
1. The fast and slow eye movements of nystagmus in crabs can be produced by moving a striped pattern around the animal or by rotating the animal in complete darkness. The discharges in the eye muscles are the same regardless of the method used to produce nystagmus. 2. Controlled irrigation of the statocyst in isolated eye-brain preparations of the crab produces activity in the eye muscles which is equivalent to the slow and fast phases of normal nystagmus. 3. When stimulated together, both statocysts combine to produce a greater excitation of the appropriate eye muscles than that produced by the stimulation of a single statocyst. 4. Anticlockwise rotation of the fluid in the left statocyst produces greater muscle activity than clockwise rotation of the fluid in that statocyst. Clockwise rotation of the fluid in the right statocyst is more effective than anticlockwise rotation in the right statocyst. 5. In a model of the system the mutual inhibitory effect between the systems driving the eyes in opposite directions is placed on the output side. The fast-phase system operates through the slow-phase systems, driving one side vigorously while inhibiting the other.

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