Abstract
It has been observed that the magnitude (b-wave) of the action potential elicited from the excised frog eyeball in response to a light stimulus varies with the magnitude of the resting potential, 1 other conditions remaining constant. It has further been reported 2 that the above direct relation was consistently observed in the dark-adapted eyes of intact curarized frogs.
These observations imply that the sensitivity of the retina, measured by the retinal electric response to a constant intensity, constant duration light stimulus, is determined by the resting potential as well as by the state of adaptation. 3 The theoretical importance of this implication indicates the necessity for quantitative data.
Method. Experiments were performed on two types of frog eye preparations: (1) excised but intact eyeballs of frogs (Rana pipiens) and (2) excised enucleated eyeballs. Electrical contact with the eyes was made through agar impregnated wick electrodes connected to calomel half cells. Resting potentials were measured with a type K potentiometer; action potentials were recorded with an Offner condenser-coupled amplifier and crystograph. All animals used were dark-adapted 24 hours or longer and preparations were made under a weak red light. Constant intensity (expressed as foot candles, hereafter f.c), constant duration (0.02 sec) test flashes were admitted at periodic intervals. Temperature varied in the range 23 to 25° C.
Results. 1. Experiments on excised intact eyeballs.
The results obtained varied with the intensity of the test flash. The protocols of typical experiments appear in Columns 1, 2 and 3, Table I. For low flash intensity (0.28 to 2.8 f.c.) the results are reasonably uniform and the ratio, action potential (b-Wave)/ resting potential is fairly constant. For flash intensity of 28 f.c. the ratio is initially high and decreases during the experiment.
Get full access to this article
View all access options for this article.