The Relation of Heart Size to the Time Intervals of the Heart Beat, with Particular Reference to the Elephant and the Whale

Abstract

ONE of the moot questions in human electrocardiography is that of the normal upper limit of the atrioventricular conduction time (PR interval) and of the duration of the spread of the excitation wave through the ventricles (QRS complex). It is the general consensus that the former may measure from 0.10 second or even a little less in the healthy newborn infant to 0.20 second or even a little more in the healthy full-grown adult, and that the latter may measure from about 0.05 second in the infant to about 0.10 second in the adult. The change from the shorter measurements . . .