THE BIOLOGY BOOK

Pulmonary Circulation

1242

The Greek physician Galen knew that blood was transported in blood vessels, that bright blood was carried in arteries and dark blood in veins, and that each had separate functions. His erroneous teaching that blood passed through the walls of the right ventricle (lower chamber) to the left side, where it picked up air and then traveled around the body, continued to be accepted for almost 1,000 years.

In 1242, the Arabian physician Ibn al-Nafis was the first to correctly describe the pulmonary circulation of blood in his book the Commentary on the Anatomy of Canon of Avicenna. He noted that there were no pores between the lower heart chambers or any direct pathways between them. Rather, he proposed that blood flowed from the pulmonary artery to the lungs, where it “mingled” with air and traveled through the pulmonary vein to the left side of the heart, from which it was distributed throughout the body. He also predicted the existence of pores between the pulmonary artery and vein, a prediction borne out four centuries later, when the Italian microscopist Marcello Malpighi first visualized capillaries.

The Spanish theologian and physician Michael Servetus was the first European to accurately describe pulmonary circulation in his Restoration of Christianity (1553), a theological work. As it was not a book of science or medicine, it was largely neglected; only three copies are extant. What was believed to be the last copy and its author were burned at the stake in Geneva, 1553, on the orders of John Calvin for Servetus’s “heretical” writings and his denial of the Trinity and infant baptism.

Realdo (also Realdus) Colombo an Italian anatomist who worked with Michelangelo, made important anatomical findings, the most significant, in about the 1550s, his discovery of the pulmonary circuit. He proposed that venous (oxygen-deficient) blood traveled from the heart to the lungs, where it mixed with air, and then the blood returned to the heart. This discovery was of great value to William Harvey when he described blood circulation in his De motu cordis in 1628.

SEE ALSO: Vesalius’s De humani corporis fabrica (1543), Harvey’s De motu cordis (1628), Blood Cells (1658).

In 1553, the Spanish physician and theologian Michael Servetus was burned alive on a pyre of his own books. These included his “heretical” theological work, Restoration of Christianity, which contained an early accurate description of pulmonary circulation.