The mode of cardiac conduction has passed through a prolonged controversial siege, but has emerged as a proven entity. The bundle of His, formerly considered as a passive agent, has now been shown to be actively engaged in generating and discharging the impulses which result in ventricular contraction (Ishihara and Nomura1). Instrumental in formulating these conclusions has been the advent of the electrocardiograph. In animals, severance of the common bundle or one of its main branches has yielded specific tracings, but its application in man is still a matter of dispute. NORMAL CONSIDERATIONS Graphically, figure 1 shows what is now considered the normal course of impulses through the heart. From the sino-auricular node, situated at the junction of the superior vena cava and the appendage of the right auricle, fibers lead to: the superior vena cava (Wenckebach's bundle), to the inferior vena cava by way of the linea terminalis