Graphic summary of the data collected from the experiments on the spread of current with various numbers of gj-channels (0, 10, 30, 100, 300, 1,000, and 3,000). Rectangular current pulses (10 nA, 5 ms) were injected intracellularly into cell #51 (near the middle of the linear chain of 100 cells), and the resulting membrane potential changes (ΔVm) were measured in the injected cell and its immediate neighbors. The myocardial cells were made inexcitable by removal of their GTABLEs. As can be seen, when there were no gj-channels, the ΔVm in the two contiguous cells (50 & 52) was nearly zero. When there were 10 or 30 channels, there was a small ΔVm in cells 50 and 52. When there were 300, 1000, or 3000 channels, the fall-off of ΔVm was exponential, i.e., the cells behaved like a long cable.