EXPERIMENTS ON THE ORIGIN AND CONDUCTION OF THE CARDIAC IMPULSE

Abstract

The criterion for sino-auricular heartblock in the mammalian heart that has been hitherto applied, both experimentally in the lower animals and clinically in man, is the occurrence of dropped beats in an otherwise regular auricular rhythm. The only exception to this comprises certain visual observations on hearts dying from asphyxia, made by Hering¹and others, the significance of which loses its value in the light of subsequent work (Eyster and Meek²). Neither the venous pulse nor the electrocardiogram in the higher animals gives evidence of activity in the sino-auricular node distinct from that of the auricle, and attempts to record by suspension methods in the exposed heart contraction of these two regions separately have been rewarded only with inconclusive results. It has seemed to us desirable therefore to carry out experimental procedures that should produce partial and complete sino-auricular block, if such conditions are indeed possible