“Greek physician Galen (ca. 129—ca. 210), was that blood was manufactured continuously in the liver and used up by the body as fast as it was made. As you will doubtless recall from your school days, the English physician William Harvey (1578–1657) realized that blood is not endlessly consumed, but rather circulates in a closed system. In a landmark work called Exercitatio anatomica de motu cordis et sanguinis in animalibus (On the Motion of the Heart and Blood in Animals),Animals), Harvey outlined all the details of how the heart and circulatory system work, in more or less the terms we understand today. When I was a schoolboy, this was always presented as one of those eureka moments that changed the world. In fact, in Harvey’s day the theory was almost universally ridiculed and rejected. Nearly all Harvey’s peers thought him “crack-brained,” in the words of the diarist John Aubrey. Harvey was abandoned by most of his clients and died a bitter man. Bryson, Bill. The Body (p. 128). Knopf Doubleday Publishing Group. Kindle Edition. Bryson, Bill. The Body (p. 128). Knopf Doubleday Publishing Group. Kindle Edition. ”