Donders vs. Harvey

Harvey [1628] published his book De Motu Cordis. In this book he rejected the theory by Galenus about the operation of the cardiovascular system and replaced it by his concept of the closed circulatory system, in which the heart provides the sole motive force. Harvey had a difficult time to gain acceptance of his ideas, but eventually he prevailed. His work remains quintessential in contemporary thinking. A few centuries later, criticism developed regarding the unique role Harvey assigned to the heart. The common feature advanced by all critics is that the heart is too weak to support the blood circulation all by itself. The critics suggested that other mechanisms serve to support the circulation. Donders, a physiologist, proposed in 1856 that the respiratory system assists the heart in its pumping effort by periodically decreasing (inspiration) and relaxing (expiration) the pressure around the thoracic vena cava. Donders' proposal resulted in a vigorous debate between opponents and proponents that lasted for more than a century without achieving a satisfactory solution. The basic question remained why the average value of blood flow should not remain the same when blood, displaced by vessel distention, could flow in from two directions, and, upon release, could flow out in those two directions in the same proportion.