When one zone of motor nerve endings is "switched off" by injecting d-tubocurarine solution into it the propagation velocity of action potentials in different regions of biarticular muscles is changed. In the middle regions of the muscle where the interference of two opposite waves of electric activity in most clearly pronounced, the "switching off" of the proximal zone of motor endings decreases the AP propagation velocity in the muscle fibres of the distal zone. When the distal zone of motor endings is "switched off" the AP propagation velocity increases. The data obtained point to the effect of electric processes in some muscle fibres on those in other muscle fibres. The degree of this effect is determined by the muscle architectonics and topography of motor nerve endings.