The influence of venous pressure upon the heart‐rate

BAINBRIDGE(1 found that increased venous filling of the heart in dogs by injection of blood or saline solution, led to a rise of venous pressure and to acceleration of the heart. He concluded that this quickening of the heart rate is reflex in origin and is due chiefly to diminution of vagus tone and partly to increased accelerator tone, since it is not necessarily or usually accompanied by changes in arterial pressure or in the respiratory movements, and it does not depend upon the character and amount of the injected fluid, except in so far as this raises the venous pressure. He found also no evidence that the activity of the suprarenal glands increased. Such a reflex must play a very important part in the circulation. It stands in contrast with the diminution of heart-rate caused by increase of arterial pressure. Prof. Starling suggested to us that we should determine whether a similar reflex occurs in the frog. As our experiments on the frog gave negative results-the explanation of which we shall give later-we repeated the experiments on the rabbit, cat and dog, and having in certain cases obtained positive results, we proceeded to investigate the parts of the heart and blood vessels from which the reflex could be obtained. It may be mentioned here that it is essential both in the frog and mammal for the injected fluid to be at the same temperature as the heart; observations on this point in the mammal have been made by Knowlton and Starling(2).