The Psycho-galvanic Reflex and Polarization-Capacity of the Skin.

Abstract

It has been shown by Gildemeister that the physiological change in the skin constituting the psycho-galvanic reflex, is a change in polarization-capacity localized in the sweat glands. Those experimenters who offer other mechanisms of the reflex have worked with inadequate apparatus. We made a study of polarization-capacity, first of metal electrodes and secondly of the surface of red blood corpuscles. In order to distinguish between resistance and polarization-capacity we measured the resistance by means of a new Wheatstone bridge and an alternating current of one and a half million cycles per second. We are able to show that the resistance of the body does not appreciably change during the psycho-galvanic reflex. We devised an apparatus whereby the impedance of the body to direct current and high frequency current could be determined simultaneously, using a condenser to shield the high frequency current from the direct current and a choke coil to shield the direct current from the high frequency current. In an average of 10 simultaneous determinations the impedance of the human body to direct current fell 13.7% and to high frequency current 0.93%. In other words, the impedance of the body to high frequency current remains practically constant during the psycho-galvanic reflex. By means of a special switch we were able to determine the high frequency impedance or true resistance of the body, and then without disconnecting the bridge, by using a current of 1000 cycles per second and taking the value of the true resistance as constant, to determine the polarization-capacity of the skin. Polarization capacity is a capacity in parallel with a resistance; for example, in one determination, the high frequency impedance was 900 ohms, and the polarizationcapacity of the resting skin was 0.035 micro-farads and 10,000 ohms.