From The Wall Street Journal:
The Greek physician Galen died in A.D. 216; his anatomic teachings went largely unopposed until the Renaissance. Even then, those who challenged them could be in for trouble. The brilliant anatomist Andreas Vesalius, to atone for crimes against orthodoxy, was forced to go on pilgrimage to Jerusalem and perished on the island of Zakynthos when his ship foundered. The Spanish physician Michael Servetus suffered a worse fate. A critic of both Galen’s anatomy and John Calvin’s theology, he was arrested in Geneva and burned alive, his books bound to his arms.
Today, every middle-schooler knows that blue blood in the veins travels to the right side of the heart and is pumped to the lungs, where it picks up oxygen and turns bright red. It then goes to the left side of the heart and is pumped into a series of progressively smaller arteries, finally traversing tiny capillaries, disgorging its oxygen and returning to the veins.
This account of the circulation of the blood took over two millennia to develop, and required demolishing dogmas that blocked the advance of science for centuries. In “The Wine-Dark Sea Within,” this process becomes a saga of heroism, villainy and high intellectual adventure, told with great eloquence and verve by Dhun Sethna, a practicing cardiologist.
Several Greeks before Galen had influential, if largely mistaken, notions regarding the circulation. Alcmaeon believed blood ebbed and flowed, instead of coursing in a circle. Praxagoras realized that the veins and arteries were separate systems, but thought the arteries carried air, not blood. This misconception may have arisen from dissections on animals that had been strangled, which led to engorged veins and underfilled arteries.
Aristotle famously blundered by asserting that the heart had three chambers, instead of four. He did, however, identify and name the aorta, the major artery that carries the outflow from the left side of the heart, and distinguished it from the vena cava. According to Aristotle, body heat was produced in the heart, which contained a sort of living fire. Aging resulted from the gradual running down of the body’s heat. Aristotle failed to see that the heart was a muscular pump. In his scheme, the motion of the heart was driven by the simmering of blood in its chambers, which made it expand.
In Galen’s model, there were two circulations. Veins arose from the liver and carried nutrition through the body, while arteries arose from the heart and carried air (pneuma), blood and heat. While these circulations were largely separate, a small amount of blood from the liver passed from the right side of the heart to the left through pores. During the Middle Ages, according to Dr. Sethna, “the proper study of the human body was a study of Galen and not the body itself . . . the tyranny of Galen, who enjoyed an almost divine authority, presented the most significant obstacle to progress in medicine.” It is unclear why Galen enjoyed such immense importance. Perhaps the durability of his dogmas was simply due to the chance survival of his voluminous writings.
The first blow to the hegemony of Galen came from Vesalius, a Flemish physician of vast energy. As a medical student, he was notorious for filching bones from cemeteries for study. As a professor, he raised eyebrows by performing dissections himself, instead of delegating the work to illiterate barber-surgeons, as was customary. Vesalius, to his dismay, found that much of Galen’s anatomy was based on animal, rather than human, dissections. He pointed out Galenic misconceptions about the anatomy of the skeleton, liver, bile ducts and uterus. Moreover, he found no trace of the pores that Galen had asserted were in the septum, the muscular wall separating the two sides of the heart.
Link to the rest at The Wall Street Journal