Electrocardiography has continued to be an active field, with studies relating to intraventricular conduction and leads or lead systems suitable for vectorcardiography contributing heavily. The important and contro versial problem is still undecided regarding the nature of excitation of the free wall of the left ventricle, namely, whether the subendocardial muscle is activated in a rapid and chaotic fashion with only the epicardial layers con tributing substantially to the QRS complex as recorded in external (direct or semidirect) leads, or whether radial spread 9f excitation occurs through the entire wall of this chamber. The group bf workers ( 1) whose studies have favored the latter view have provided no further evidence to support it, but in investigations using the same techniques, have shown that in the dog with left branch block the septum is excited from right to left, with the left ventricle activated earliest on the anterior, epicardial aspect. The latter causes excitation to pass inward toward the cavity of the left ventricle for a short time. In experimental studies and limited observations on the human heart directed toward an analysis of the form of the QRS complex in epicar dial leads, Pipberger and his associates (2) have confirmed their earlier im pression that only the outer layers of the left ventricle contribute signifi cantly to the R wave seen in: epicardial leads. The implications of these observations, particularly in myocardial infarction, were pointed out and in this connection, the frequent occurrence of a QRS complex with a small initial r wave and large S wave (rS) in the epicardial lead over an infarct was mentioned. Sodi-Pallares and his colleagues (3), in ingenious experimental studies, attempted to relate pathways of ventricular activation to findings in vector cardiograms. This was done by determining the locations of maximal posi tivity and negativity on the epicardial surface of the ventricles at a number of instants of time during excitation. These they designated as the apparent maximal potential gradients and, when represented by vectors, made it possible to construct vectorcardiograms in the three usual planes. These vectorcardiograms were compared with vector figures recorded by the use of the cube system of electrode placement, and agreement was sufficiently close to justify the conclusion that vectorcardiograms give valuable in-