1628
Around 1600, an old model of the blood system still held sway. William Harvey (1578-1657) published his "Exercitatio anatomica de motu cordis et sanguinis in animalibus" (An Anatomical Essay Concerning the Movement of the Heart and the Blood in Animals) in 1628, revising outdated understandings. Contrary to earlier work, Harvey concluded that the heart's beating, rather than an intrinsic "pulsative virtue" of the blood vessels, was responsible for the pulsing of arteries. More importantly, whereas earlier models of the blood system asserted that blood was continuously absorbed by the body and replaced by the liver, Harvey's experiments showed that more blood flowed through the heart in one minute than could possibly be created by the body in the same amount of time. In other words, rather than being absorbed immediately, blood flowed in a continuous circuit through the heart, lungs, and body.