In the main electric organs of the electric eel, the cross-sectional area, the thickness of the electroplaxes, and certain electrical characteristics of the tissue vary widely between the anterior and posterior ends. However, a transverse layer of the organs one electroplax thick has certain characteristics which are roughly uniform along the organs. These are its volume, its maximum voltage, its maximum current per unit area, and the resistance of unit area at the peak of the discharge. Measurements of the voltage developed by a segment of the organs across different external resistances at different instants during the discharge are all rather well described by representing the segment, with the adjacent non-electric tissue, as a simple combination of E.M.F. and ohmic resistance. The internal resistance of the tissue varies during the discharge. Its E.M.F. appears to be practically constant, at least during the greater part of the discharge. Estimates made of the total electric energy show it about equal to the energy supplied by the decrease of phosphocreatine and the formation of lactic acid.
The electrical potential profile of the isolated toad skin was recorded, in vitro, by impalement with micropipette-electrodes, when both sides of the skin were bathed with sulfate-Ringer. The outer side of the skin was some 110 mv negative with respect to the inner side. Upon impalement from the outer side, two main positive steps of 40 to 70 mv each were found to form the skin potential. The site of measurement of each potential difference was permanently marked in the tissue during recording, by deposition of carmine from the micropipette tip using iontophoresis. Serial histological sections of the skin were prepared and search was then made of the carmine deposits 2 to 6 µ in size, under phase contrast microscopy. By this method the main steps were located at the outer and the inner sides of the stratum germinativum cells. The DC resistances between the micropipette tip and the bathing solutions were measured during the recording of each potential difference. The resistance at the outer side of the stratum germinativum cells, of 1.09 kilohm. cm2, was larger than that at their inner side, of 0.30 kilohm. cm2. The stratum germinativum cells maintained a potential difference of -34 mv during short-circuiting of the skin.