BUNDLE-BRANCH BLOCK In 1910, Eppinger and Rothberger1 published electrocardiographic tracings illustrating the effects of dividing the right and left branches of the His bundle on the ventricular complex. Eppinger and Stoerk,2 later in the same year, were able to report two clinical cases of bundlebranch block in which the diagnoses, made with the aid of electrocardiograms, were confirmed at section. Since that time similar cases have been reported by a large number of authors. Carter,3 in his report of twenty-two cases, concludes that the ventricular complexes seen in cases of bundle-branch block exhibit, in contrast to normal ventricular complexes, the following characteristics. They are diphasic rather than polyphasic and are composed of (1) a primary deflection or QRS group, whose amplitude is greater than that of the normal ventricular complex and whose duration is longer, being one-tenth second or more; and (2) of a secondary