Source / Experimental anatomical book
William Harvey's 1628 Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus argued that the heart propelled blood around the body in a continuous circulation.
The compact Latin book built its case through repeated observation, animal experiment, ligatures, the direction of valves, quantitative reasoning, and challenges to inherited accounts of the heart and blood.
Reading the source
Harvey did not rely on a single decisive experiment. He moved among visible heart motion in different animals, dissection, manipulation of vessels, estimates of blood volume, and simple demonstrations readers could repeat on a living arm.
In slowly beating or exposed animal hearts, Harvey identified systole as the forceful contraction that expelled blood. The arteries expanded after the ventricular beat because they received blood, not because they actively drew it in. Sequence and touch allowed motion to be analysed where rapid action had confused observers.
Harvey estimated how much blood the heart expelled with each beat and multiplied that amount over time. Even deliberately conservative figures produced more blood than food could continually replace. If the body did not manufacture and consume such volumes, the same blood must return and move repeatedly.
A tight band stopped arterial inflow, while a looser one allowed the arm's arteries to fill and veins to stand out. Pressing blood along a visible vein showed that its valves permitted movement toward the heart but resisted the reverse. These demonstrations connected anatomical structure to one-way flow.
Argument and limits
Harvey could demonstrate that blood somehow crossed from the arterial to the venous side in the body's tissues, but he could not see capillaries. Microscopic observation later supplied structures that made the connection visible. The book's power lay partly in arguing for a necessary link before the available instrument could show it directly.
The account challenged Galenic physiology but did not emerge outside earlier scholarship. Harvey studied at Padua, where anatomical teaching and work on venous valves shaped his questions. Earlier authors, including Ibn al-Nafis, had criticised aspects of Galen and described pulmonary transit. The history of circulation is larger than a single European publication.
Animal vivisection generated otherwise inaccessible evidence while inflicting suffering. The text offers a source for the history of experimental method and for the ethical costs hidden inside demonstrations. Its persuasive order also reminds readers that published experiments are selected narratives, not unmediated access to everything that occurred.
Across the collection
Follow Harvey's education, lectures, court medicine, experiments, publications, supporters, and critics.
Place the 1628 publication and its evidential programme on the chronological spine.
Connect dissection and structure to experiment, motion, instruments, illustration, and physiological explanation.