Servetus and the Circulation of Blood

Harvey’s anatomical demonstration of the circulation of the blood, in 1628, opened a new path in the history of medicine. Yet, while the anatomical demonstration was truly groundbreaking, the idea that the blood could circulate was not.

As shown by Walter Pagel, from Ibn al-Nafis to Realdo Colombo, Michael Servetus, and Andrea Cesalpino, many physicians had already tinkered with this idea before. While briefly touching on their individual merits, in this lecture I will deal specifically with the contribution of Michael Servetus (c. 1509–1553) on this subject.

A Spanish theologian and physician, Servetus is remembered nowadays mostly for two things: having been executed for antitrinitarian and anabaptist heresy by the Genevans under Calvin, and having published a work titled Christianismi restitutio containing a description of the transit of the blood through the lungs.

Printed in early 1553, the Restitutio survived only in three copies, leaving Servetus’ work unnoticed by medical scholars for well over a hundred years, until it was rediscovered in the eighteenth century by the French Encyclopedists, Diderot and D’Alembert, who credited Servetus with the discovery of the circulation of the blood before Harvey.

By examining Servetus’ work, in this lecture I will argue that this attribution was anachronistic and that Servetus’s idea of circulation seeks to resolve a theological rather than an anatomical dilemma: how the soul entered the body.