Experimental Modification of the Polarity Potential of the Human Eye *

A relatively steady resting potential in the extirpated eyeball of cold-blooded animals was independently discovered and reported by Holmgren3" 4 and by Dewar and McKendrick7 more than a half-century ago. Later investigators, among them Kuhne and Steiner,2' Waller,32 Gotch," Bossa and Kohlrausch,2 and Kohlrausch,19 extended the observations on this subject by various studies on several animal forms including certain mammals. This field of investigation, including both the steady potential, which is not primarily dependent on light stimulation, and the transitory or action potential, which does depend on luminous stimuli, has been comprehensively reviewed by Kohlrausch.20 The first recorded effort to register potentials from the normal human eye appears to have been only moderately successful. It was reported by Dewar' in 1877. A small trough of clay or paraffin was constructed around the margin of the orbit so as to contain a quantity of dilute salt solution when the body was placed horizontally and the head properly secured. Into this solution the terminal from a non-polarizable electrode was introduced and the other electrode was connected with a large trough containing salt solution into which one of the subject's hands was inserted. Dewar reports: "By a laborious process of education it is possible to diminish largely the electrical variation due to the involuntary movements of the eyeball, and by fixing the eye on one point with concentrated attention, another observer watching the galvanometer, and altering the intensity of the light, can detect an electrical variation similar to what is seen in other animals. This method, however, is too exhausting and uncertain to permit a quantitative observation being made." Dewar's interest was primarily in measuring the retinal action current resulting from the stimulation of the eye with light. He notes that the