Abstract
Studies of the tortoise heart in situ were made with a view to determining the extent to which ventricular filling is due to auricular systole. From observation it was obvious that such an effect existed, although it was difficult to show by means of a kymograph and lever system.
The cinematographic method, originally employed by Takeuchi 1 and Strughold 2 and lately Gray and Steggerda, 3 was used to record size changes and resulted in a clear picture, free from artifacts of inertia and overthrow common to mechanical systems. Pictures were taken at 8 per second and various diameters of the ventricle and auricle in each picture were measured under a binocular so that any change in diameter could be plotted graphically and used for further study.
In a typical curve from a slowly beating heart there is shown a definite increase in ventricular size just prior to systole. In all cases this coincides with the contraction of the auricles as indicated by the curve of auricular diameter. To examine the possibility that this auricular effect might be exaggerated by the absence of the restraining influence of the pericardium, experiments were done in which the beating heart was photographed through the pericardium. The measurements showed no difference between these hearts and those in which the pericardium had previously been removed. To further test the validity of this auricular effect on ventricular filling, the auricles were ligated in such a manner as to allow a clear passage for the blood from the sinus venosus to the ventricle, but at the same time preventing blood from entering the fundus of the auricles. By this operation, the mechanical effect of the auricular systole was abolished without impeding the path of either the blood or the excitation wave.
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