X. The excitatory process in the dog’s heart. Part I. —The auricles

The experiments, of which this paper is a report, were undertaken with the object of establishing more fully the point of origin of the contraction wave in the mammalian heart, and of unravelling the course which this contraction wave follows in the auricles. As the history of this subject has been summed up but recently by one of us (10), we do not propose to consider it in detail at present. In studying the heart from these points of view, we have adopted the electrical method as being the most accurate at our command, and have investigated the wave of excitation which, though it actually precedes the wave of contraction, is closely associated with the latter. We deal, therefore, with the origin and propagation of the excitatory process in the heart, accepting the information which we so gather as an index of the origin and course of the contraction wave.