Electrocardiograms were obtained at intervals from an old hemiplegic patient who was known to have complete heart-block from February 26, 1912, up to the day of his death, December 31 of the same year. During many months of this period he had pronounced Cheyne-Stokes respiration. The interest in this case lies in the fact that there were frequent changes in the electrical complexes of the ventricular beat and correlated with this the fact that histological examination revealed no organic lesion to account for the block, in the auriculo-nodal junction, the node of Tawara, or the main stem and its branches. The nodal artery was sclerotic.The variations in the ventricular complexes were seen not only from one examination to the next, but often from beat to beat.The waves Q, R, S and T all showed variations; for example with leads I and II the wave R was sometimes upright, sometimes inverted. With lead III the wave R was always inverted.The auricular rate was strikingly reduced during the dyspneic period (44....