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In this study, the normal ballistocardiogram is interrelated with various cardiac events

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There has been considerable difference of opinion during the development of electrocardiography as to the relationship between the electrical phenomena of the heart beat, as recorded by the electrocardiograph, and the attendant muscular activity. It has come to be generally held that the waves of the electrocardiogram indicate the spread of relative electrical negativity throughout the heart from the region of the sino-auricular node to the various parts of the heart's musculature. The electrical energy propagated in this manner has been the expression of the so-called "excitation wave."Much physiological research has been undertaken in an attempt to demonstrate the time relationship between this "excitation wave" and the muscular contraction of the heart. In general most of such work has been by the method of simultaneous registration of electrocardiographic and myocardiographic records in such a manner that they can be compared, and the sequence of events studied and measured. Similar comparisons have been made between electrocardiograms and intracardiac pressure curves. Myocardiographs have been devised by Cushny, Roy, Gesell, Wiggers and others, and have been used in connection with the string galvanometer, for which we are indebted to Professor W. Einthoven.By the extensive researches of Garten and Weber, Wiggers, Lewis, Feil and Stroud, Wiggers and Dean, and others, it became generally recognized that the "excitation wave" precedes the muscular contraction of the heart by a definite and constant interval. Wiggers (1)