Since Eppinger and Rothberger, in 1910, reported their experimental work on dogs in which the right and left branches of the His bundle were severed, a large volume of literature on this subject has accumulated. In recent years several workers have analyzed case records in an effort to determine what if any are the prognostic implications of electrocardiographic evidence of bundle branch block. Among the more recent of these surveys have been those of Willius,1King,2Wood,3Graybiel and Sprague4and Sampson and Nagle.5In 1934 Wilson and his co-workers,6experimenting with serial precordial leads for human beings and with curves obtained after section of the right bundle branch in dogs, were able to show that certain electrocardiographic patterns, previously not fully understood, represented right bundle branch block in man. These workers7described "electrocardiograms of an unusual type" which also were thought to be representative of right