William Harvey & The Mechanics of Blood Circulation (1628): De Motu Cordis and the Cardiovascular Hydraulic Circuit

The Mathematical Demolition of Humoral Cardiology

Before 1628, medical doctrine taught that blood was manufactured continuously in the liver from digested food, pumped outward to peripheral tissues via the veins, and completely consumed like fuel in a fire. In his 72-page masterpiece, Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (On the Motion of the Heart and Blood in Animals), English physician William Harvey (1578–1657) proved this theory mathematically impossible.

1. The Quantitative Stroke-Volume Calculation

Harvey applied quantitative mathematical modeling to human physiology:

• The human heart pumps approximately 2 ounces (60 mL) of blood with every beat.


• At 72 beats per minute, the heart outputs 8,640 ounces (259 liters / 540 pounds) of blood per hour—vastly exceeding the entire weight of the human body.


• Where could such an immense volume of blood come from, and where could it go? Harvey concluded: The blood must move in a continuous, closed circular loop.

2. Experimental Proof with Tourniquet Valves

By applying simple tourniquets to the human forearm, Harvey demonstrated that venous valves (Fabricius valves) permit blood to flow exclusively in one direction: toward the heart.

3. References & Historical Citations

• Harvey, W. (1628). Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus. William Fitzer, Frankfurt.
• Keynes, G. (1966). The Life of William Harvey. Clarendon Press, Oxford.

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