Who Discovered the Pulmonary Circulation? Servetus, Valverde or Columbo?

In 1559. the year of his death. Italian physician and surgeon Realdo Colombo published De re anatomica libri XV in Venice.  Colombo's work is best known for his discovery of the pulmonary or lesser circulation, i.e., the passage of blood from the right cardiac ventricle to the left via the lungs. Although this discovery was first published in Rome in the Historia de la composicion del cuerpo humano (1556) by Colombo's friend and former pupil Juan Valverde de Hamusco, the evidence in both Valverde's and Colombo's accounts indicates that the discovery was Colombo's, made through his vivisectional observations of the heart and pulmonary vessels. Colombo's account of the pulmonary circuit was preceded by that in Michael Servetus's Christianismi restitutio, and by the thirteenth-century account of  Ibn al-Nafis. However, because Servetus's Christianismi restitutio (1553) was completely suppressed, and Ibn al-Nafis' work was not published in print until the early 20th century, there is no evidence that either was available to Colombo at the time.

Colombo's observations of the heart also enabled him to gain a more correct understanding of the phases of the heartbeat, generally confused by his predecessors, who erroneously likened the heart's action to the expansive action of a bellows. Although overshadowed by his discovery of the pulmonary circulation, Colombo's observations of the heartbeat apparently directly inspired Harvey's vivisectional studies on the heart, which in turn led to his discovery of the greater circulation.

Colombo evidently died during the printing of his work, since in most copies his original dedication letter to Pope Paul IV (who also died while the work was in progress) has been replaced with a dedication to Pope Pius IV by Colombo's two sons, mentioning their father's recent demise. According to tradition, the work was to have been illustrated by Michelangelo; however, Michelangelo left no drawings or any other evidence that he ever seriously considered the task, and we can only speculate as to what sort of artistic masterpiece he might have produced. Colombo's book was published without illustrations except for the woodcut title, which was inspired by that of Vesalius's Fabrica. Schultz (p. 103) points out that the dangling right arm of the cadaver in the title-page woodcut recalls Donatello's bas-relief, The Heart of the Miser.

Schultz, Art and Anatomy in Renaissance Italy (1985) 102-104. Hook & Norman, The Haskell F. Norman Library of Science and Medicine (1991) no. 501.