A text-book of physiology, for medical students and physicians . chamber closedeverywhere except at the outlet to the recording change in volume of the ventricles will be recorded accu- ? Henderson, American Journal of Physiology, L6, 325, L906, and23, 345, L909, contain also the literature. THE HEART BEAT. 529 rately provided there is no leak. Moreover, these volume changesmay be given absolute values in cubic centimeters if the appa-ratus is calibrated beforehand. The cardiometer furnishes aconvenient method of estimating directly the amount of bloodentering and leaving the ven
A text-book of physiology, for medical students and physicians . chamber closedeverywhere except at the outlet to the recording change in volume of the ventricles will be recorded accu- ? Henderson, American Journal of Physiology, L6, 325, L906, and23, 345, L909, contain also the literature. THE HEART BEAT. 529 rately provided there is no leak. Moreover, these volume changesmay be given absolute values in cubic centimeters if the appa-ratus is calibrated beforehand. The cardiometer furnishes aconvenient method of estimating directly the amount of bloodentering and leaving the ventricles under varying conditions,as well as the changes in heart-volume that may result fromvariations in tonicity. When the heart is beating slowly thevolume curve has the form shown in Fig. 224. During systolethe ventricles shrink in size as the blood is discharged into theaorta and pulmonary artery—the up-stroke of the curve. Atthe end of the systole, after the closure of the semilunar and theopening of the auriculoventricular valves, the ventricles are. i Fig. 224.—Diagram of the normal volume curve (plethysniogram) of the dogs heartwhen beating at a slow rate (after Hirschfelder). The up-stroke represents the systole,the down-stroke the diastole; 4 to 5 the period of diastasis (Henderson). At 5 the auricularcontraction causes a slight additional dilatation of the ventricle. 1, 2, and 3 represent thetime of occurrence of the first, second, and third heart-sounds respectively. dilated rapidly by the inflow of venous blood. Henderson hasemphasized the fact that the filling takes place nearly as rapidlyas the emptying, owing doubtless to the fact that at the end ofventricular systole the auricles are dilated under some pressure,so that their contents escape at once into the ventricles as soonas the intervening valves are opened. The diastolic curvecomes back nearly to the base line and then forms a shoulder(4) from which it runs parallel to or approaches gradually tothe ba
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