SummaryA study of 15 normal subjects has been performed by using fluorocardiog-raphy, a method which permits recording on a continuous film of the pulsations of various cardiovascular structures revealed by the x-ray. (a) The tracing of the ascending aorta presents a typical pattern which partly is due to transmission of intraventricular pressure and partly to motions of the aortic root connected with ventricular systole and diastole. (b) It is possible to record in certain cases a tracing of the pulmonary veins. Its most typical feature is a positive wave during presystole, (c) The velocity of the pulse wave in the lesser circulation is much lower than in the greater circulation. It is more rapid in the smaller branches than in the stems of the pulmonary artery. Average figures are given, (d) The tracing of the pulmonary parenchyma is the equivalent of a pie thy sinogram. While the rise and the ascending branch of the wave are of arterial pulmonary origin, the peak and the descending branch of the wave a...