THE SEQUENCE OF FRACTIONATE CONTRACTION AT DIFFERENT SURFACE REGIONS ON THE RIGHT AURICLE AND VENTRICLES OF THE DOG'S HEART

Abstract

Differential potential-like curves are recorded from different surface regions of the right auricle and ventricles of the dog''s heart, along with a reference curve, by means of direct current amplifiers and oscillographs. The onset of fractionate contraction in a region is coincident, within errors of measurement, with the main peak of the differential curve. The first regions entering into fractionate contraction on the surface of the right auricle are those contiguous with the upper part of the sulcus terminalis and from here contraction proceeds in rather regular fashion to the appendage and downward to the auriculo-ventricular junction. The interval between the 1st and last regions involved is of the order of .03 sec. In the ventricles, the 1st surface contractions appear on the right ventricle contiguous to the auriculo-ventricular junction. Other regions enter into contraction in a manner which fails to show any evidence for a progressive involvement such as exists in the right auricle. The interval between the first and last regions involved is of the order of .02 sec. The fact that no criterion exists at present for the detn. of the onset of "excitation," which presumably precedes the contraction of a region, is discussed.