MOVEMENTS OF THE BASE OF THE VENTRICLE AND THE RELATIVE CONSTANCY OF THE CARDIAC VOLUME

The view that1 tlhe heart remains relatively constant in volume in diastole as in systole, has been maintained by one of us on the basis of an analysis of tjhe cardiopneumogram (1). Thus cardiac volume changes produce pressure changes within the lungs which, when transmitt,ed through the respiratory t,ree and corrected for tlhe elastic give of the chest walls, seem to be produced by a cardiac volume change of 1 or 2 cc., (certainly less than 7.5 cc.) and last through only a part of systole. This has been confirmed in part by E. Holzlijhner (2) who admits that the net systolic decrease in intrathoracic blood volume is small (5 cc.) but insists that much larger quantities of pulmonary air (25-30 cc.) are displaced by changes in intrathoracic blood volume during the course of syst,ole. That the quant’ities of air which move in and out of the chest during the cardiac cycle are of the order of 1 or 2 cc., is easily demonst,rat#ed by a simple experiment. If one fills the mouth with smoke and maintains respiratory standstill with the internal nares closed and the glott,is open, a t,iny puff of smoke is seen t’o issue from the lips toward the end of each ventricular systole. The amount of this is usually not more than 0.5 cc. as contrasted with Holzlohner’s figure of 25 to 30 cc. Teleologically one might well expect that the heart is organized so as to move blood and blood alone. It does not wast’e energy moving the contiguous tissues about. The heart? is able to pump blood without much displacement of contiguous tissues through the fact that its major pumping action is due to the caudo-cephalad movement of the atrioventricular septum. This in turn insures t’he reciprocal action of t,he two chambers so that the auricles fill during ventricular systole, and ventricular filling occurs at t’he expense of a reduction in the volume of the auricle. It has long been known that the base of the ventricle makes a large excursion toward t!he apex during systole and that the apex makes little move-