Galen (c.130-c. 200)

Greek physician and anatomist whose ideas dominated Western medicine for almost 1,500 years. Central to his thinking were the theories of humours and the threefold circulation of the blood. He remained the highest medical authority until Andreas Vesalius and William Harvey exposed the fundamental errors of his system. Galen postulated a circulation system in which the liver produced the natural spirit, the heart the vital spirit, and the brain the animal spirit. He also wrote about philosophy and believed that Nature expressed a divine purpose, a belief that became increasingly popular with the rise of Christianity (Galen himself was not a Christian). This helped to account for the enormous influence of his ideas. Galen was born in Pergamum in Asia Minor and studied medicine there and at Smyrna (now Izmir), Corinth in Greece, and Alexandria in Egypt, after which he returned home to become chief physician to the gladiators at Pergamum. In 161 he went to Rome, where he became a society physician and attended the Roman emperor Marcus Aurelius Antoninus. Although Galen made relatively few discoveries and relied heavily on the teachings of Hippocrates, he wrote a large number of books, more than 100 of which are known. The dissection of human beings was then regarded as taboo and Galen made inferences about human anatomy from his many dissections animals. His detailed descriptions of bones and muscles, many of which he was the first to identify, are particularly good; he also noted that many muscles are arranged in antagonistic pairs. In addition he performed several vivisection experiments; for example, to show that urine passes from the kidneys down the ureters to the bladder. More important, he demonstrated that arteries carry blood, not air, thus disproving Erasistratus' view, which had been taught for some 500 years.