This Doctor Upended Everything We Knew About the Human Heart

In the 17th century, English doctor William Harvey tore down theories that had been popular in Europe for nearly 1,500 years.

Until 1628 few Europeans disputed the teachings of Galen, an accomplished Greek physician and scholar. Galen lived in the second century A.D., and his teachings would come to dominate European medicine and scholarship for centuries.

Galen’s massive contributions to medicine cannot be denied. He was the first to identify the physiological difference between veins and arteries. He also disproved a 400-year-old theory that arteries conveyed not blood but air throughout the body (the name artery comes from this original idea: The Greek arteria means that which conveys air”). By the 16th and 17th centuries scientific methods had evolved, making it easier for new scientists to challenge the old ones. Galen’s theories were sitting ducks, waiting for a physician like Englishman William Harvey to take them down.

Galen taught that there are three main interconnected systems in the body: the brain and nerves; the heart and arteries; and the liver and veins. According to Galen, dark, venous blood formed in the liver and then traveled through the veins throughout the body to deliver nourishment and build and maintain tissues. Some blood would come into contact with air in the lungs and go to the heart. From there, this bright red blood went to the brain to form “pneuma,” a substance responsible for sensation and feeling.

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