Initially, a brief representation of the anotomical circumstances and excitation propagation is given. By applying the 1st and 2nd ligatures of Stannius the conducting pathway is interrupted. This has the effect of activating secondary and tertiary pacemaker centers. Electrostimulation of the ventricle and the lower leg of the frog proves that the cardiac musculature, in contrast to the skeletal musculature, is non-tetanizable. Electrostimulation of the parasympathetic and sympathetic fibres of the vagus nerve produces characteristic modifications of cardiac excitation generation and conduction.