In the course of a study of the pharmacologic reactions of the human eye,1which was conducted as a part of the series of studies on human autonomic pharmacology, our attention became directed to the autonomic pharmacology of the Argyll Roberston pupil. One of us (A. M.) had observed that in the case of a patient who had tabes dorsalis and was under treatment for an anxiety neurosis of independent nature benzedrine sulfate, administered in doses of 20 mg. per day, gradually dilated the pupils and brought about a condition in which there was a partial reaction to light. This formed the starting-point of a series of researches on the Argyll Robertson pupil,2of which this paper is a preliminary communication. Argyll Robertson himself defined the pupil which now forms a landmark in medicine as having four essential factors: (1) the pupil is small; (2) there is absence