Harvey Shows the Blood Circulates
A 72-page book in 1628 recasts the heart as a pump and blood as a closed loop, undoing Galen for good
Quick facts
- Author
- William Harvey
- Published
- 1628, as De Motu Cordis
- Length
- 72 pages
- Claim
- Blood circulates in a closed loop, driven by the heart as a pump
What happened
In 1628 William Harvey published his account of the movement of the heart and blood, a slim 72-page, poorly bound paper edition riddled with printing errors, known by its short Latin title De Motu Cordis. In it Harvey argued that the blood is driven round in a circular motion and moves perpetually, and that the heart performs this circulation by its pulsation, acting as a pump. This overturned the Galenic picture, which held that blood was continuously made in the liver and consumed by the body, and that some seeped through invisible pores in the wall between the heart's chambers. Harvey used measurement and experiment to show that the sheer volume of blood the heart moves could only be explained if the same blood circulated again and again through a closed system.
Why it matters
Harvey's circulation is a model of how quantitative reasoning can settle a question that pure observation could not. By calculating how much blood the heart pumped, he proved circulation had to exist even before the tiny capillaries linking arteries to veins could be seen, and he replaced a 1,400-year-old theory of the blood with one that is essentially correct, giving physiology a firm mechanical foundation.
How we know
De Motu Cordis survives in its 1628 edition and later printings, and Harvey's argument, including his quantitative reasoning and his explicit rejection of Galenic pores in the heart, can be read directly in the text and is analyzed in the medical-history literature.
Sources
- Journal of the Royal Society of Medicine (via PMC / U.S. National Library of Medicine). De Motu Cordis: the Lumleian Lecture of 1616 · Peer-reviewed (author-declared)pmc.ncbi.nlm.nih.gov · Cited as a "journal" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- Journal (via PMC / U.S. National Library of Medicine). Harvey, by Hercules! The Hero of the Blood's Circulation · Peer-reviewed (author-declared)pmc.ncbi.nlm.nih.gov · Cited as a "journal" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
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Related timelines
- The Scientific Revolution → · Harvey's use of measurement and experiment to overturn ancient theory is part of the broader change covered in the Scientific Revolution timeline.