This illustration from William Harvey's 1628 De Motu Cordis shows how valves in the veins of a human arm allow the blood to flow towards the heart, but not away from it. __1657: __The blood stops circulating in the body of the scientist who definitively established that blood indeed circulates. William Harvey is dead.
Most scientists and physicians in Harvey's time were still blindly following the second-century Greek physician Galen, who proved that arteries contain blood. But he thought that the liver converted food to blood and that the arteries and veins are distinct systems. Galen warned his students not to be content with book knowledge, but 14 centuries of doctors relied instead on Galen's many anatomical treatises and did not themselves perform dissections.
In the century before Harvey, Belgian anatomist Andreas Vesalius published charts of his own dissections. Vesalius' work literally resurrected the practice of dissection of human cadavers: It was still widely forbidden, and for centuries to come often had to be performed in secret on newly dead bodies stolen from cemeteries by "resurrection men."
Cairo physician Ibn al-Nafis had established the "lesser circulation" between heart and lungs in the 11th century. Hieronymus Fabricius, of Italy, published a work on the valves in the veins in 1603, but he mistakenly saw them as imposing a speed limit on the flow of blood from the heart. However, al-Nafis' work was not widely known in Christian Europe, and no one put it together with the true import of Fabricius' research.
Until William Harvey.
Harvey experimented on animals and even on surface veins in the limbs of living humans. In 1628, he published his magnum opus, Anatomical Disquisition on the Motion of the Heart and Blood in Animals -- often called De Motu Cordis for the literal heart of its original Latin title.
It demonstrated conclusively that the heart pumps blood to the rest of the body, and that the veins return the blood to the heart. With the microscope not yet available, Harvey could not see what connects the smallest arteries to the smallest veins, but he postulated the existence of the capillaries.
Harvey also served as a royal physician. How did he get a plum job like that? The man was talented, but he also had the good judgment to marry the daughter of another royal physician.
As doctor to King Charles I, Harvey did a lot of scrambling during the English Civil War, losing most of his scientific papers and ordinary possessions to anti-royalist riots. He fled London to Oxford with the court in 1642, then left the court (and his job) to return to London in 1646. Thus, he was not royal physician when the king was beheaded in a public execution on a London street in 1649. Plenty to learn about the motion of blood there.
Harvey published his second major work, On Generation in Animals, in 1651. In it, he propounded the notion that an animal embryo grows gradually, in parts, and does not exist fully formed in miniature in the ovum, as much current theory then held. Harvey's ideas, as with circulation, were based on direct observation and measurement.
But the founder of modern experimental physiology, cardiology and embryology was again impeded by not being able to observe the microscopic level: the earliest, smallest stages of embryonic growth. Antony van Leeuwenhoek did not make the first practical microscopes until two decades after Harvey's death.
Harvey died at age 79. The cause of death was a stroke, which we now know to be a circulatory disease.
Source: PBS' Red Gold
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