Voltage/current curves obtained for myocardial cell # 51 near the middle of the single linear 100-cell chain. Depolarizing and hyperpolarizing rectangular current pulses (duration of 5 ms and intensities of 2, 6, and 10 nA) were injected intracellularly into cell #51 and the resultant voltage changes in that cell were recorded and plotted. The ΔV0/I0 curves were linear, in both the depolarizing and hyperpolarizing sectors, because rectification was not incorporated into the basic membrane units that composed each cell. The number of gj-channels connecting the contiguous cells was varied from zero to 3000, but only two of the curves are illustrated, namely for zero and 1,000 gj-channels. As predicted, the curve for 0 gj-channels had a steeper slope and higher input resistance (Rin) than the curve for 1000 gj-channels, namely 29.4 MΩ versus 8.4 MΩ.