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Abstract
The sphincter iridae and ciliary muscles of the alert monkey differ in their frequency response to intracranial electrical stimulation of the third nerve. Unilateral pupil constriction falls off when stimulation frequencies exceed 100 Hz., but brisk accommodation responses are obtained up to at least 1,000 Hz. Electrical stimulation of the short ciliary nerves in the anesthetized monkey produces good responses in both sphincter iridae and ciliary muscles to frequencies of at least 1,000 Hz. Local application of nicotine to the ciliary ganglion abolishes pupil constriction, but not accommodation, on electrical stimulation of the third cranial nerve proximal to the ciliary ganglion. It is concluded that the motor pathway for accommodation does not have a synapse in the ciliary ganglion while that for pupil constriction does.