Introduction The present study is the first of a series concerning the circulatory forces responsible for the motions of the heart and of the body in health and in disease. Ideally, such investigations should deal first with the normal motions in order that limits may be established for the recognition of abnormalities. However, the normal motions are complex, and in some instances their interpretation is facilitated by the simultaneous study of certain abnormal states. In the first several publications in this series, the movements, as observed in normal subjects, will be emphasized, and abnormal conditions will be considered only in so far as they may aid in understanding the findings in the normal persons. The movements of the heart as reflected in tracings from the precordium are numerous and complex. Only one such movement is ordinarily detectable by physical examination. This is, of course, the apex beat. Hence this movement