The development of His-bundle (H) electrocardiography and the concept of hemiblocks have prompted a re-examination of conventional thinking about the indications for treatment of atrioventricular (AV) block. The technic of treatment is not the issue; ventricular pacemaking is the only really effective and reliable method. The problem for this review is what these recent developments have contributed to deciding when and if a pacemaker should be installed.

Like general medicine, clinical genetics has responsibilities to research, to dissemination and to service. Each exists at three broad levels. The elemental comprises acquisition of fact and development of technics. At the intermediate level coherence becomes a major concern: the discernment of relations among facts; the incorporation of data into ideas and insights; organization of clinical findings into a diagnosis; and the development of the rational management. The sophisticated level calls for theories and cosmologies at the scientific level, and cultivation of scholarship and of clinical wisdom. All nine compartments should be mutually correcting. If any of them is neglected or isolated from the rest, the whole will be impoverished-the student will suffocate in disconnected, empirical facts; fanciful theories will be spun from tenuous evidence; well established theory will be neglected by the practitioner; the best-intentioned schemes will have disastrous long-term consequences.