Illustration of the 16th Century Spanish physician Michael Servetus (1511-1553), also known as Michel Servet. As a physician, Servetus was the first European to describe the function of the pulmonary circulation, though it was not widely known at the time as it was published in the theological work 'Christianismi Restitutio' in 1553. His theological thoughts were ultimately condemned as heretical, and he was burnt at the stake near Geneva, Switzerland. Illustration from 1837.