CASE REPORTS THE SIGNIFICANCE OF SPLITTING OF THE P-WAVE IN THE ELECTROCARDIOGRAM *

NOTCHING, bifurcation and splitting of the P-wave have been observed in a variety of cardiac conditions. The feature which is common to all and which is responsible for the abnormality can best be understood by considering a few facts relative to the time of onset of the contraction of the two auricles and the modifications that follow experimental interference with the spread of the wave of excitation from one auricle to the other. An old observation of Chauveau x made on the horse in 1894, that the right auricle contracts before the left, was confirmed experimentally by Fredericq 2»3 using the dog's heart, and subsequently by his pupils Schmidt-Nielsen4 and Stassen,5 who found a time interval of 0.03-0.04 sec. Garten 6 a/id Erfmann7 obtained by local derivation of the action current, an interval of 0.013-0.014 sec. Lewis, Meakins and White 8 concluded from their measurements that the ques-tion as to whether right or left auricle first contracts is unprofitable since " certain portions of the right auricle contract before certain portions of the left auricle, and vice versa. " But, as was pointed out by the writer,9 although it is doubtles