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Harvey's discovery of blood circulation
1628 (De Motu Cordis)· Invention or discovery· Medicine & surgery
Well documentedSolid records, physical evidence or scientific consensus.
William Harvey's 1628 proof that the heart pumps the same blood around the body in a continuous loop.
See it on the Technology & Medicine map →How it works
Galen had taught that the liver made blood from food and the body used it up. Harvey, an English physician trained at Padua, estimated the heart's output: it pumps far more blood in an hour than the whole body weighs, so blood must be recycled. Tying cords around arms showed that arteries carry blood away from the heart and veins, with one-way valves, carry it back. He could not see the capillaries joining them; Malpighi found them with a microscope in 1661.
Why it mattered
It replaced a 1,400-year-old model with one based on measurement, and underpins later medicine, from blood pressure and transfusion to heart surgery.
Think of it like
Like a closed-loop hot-water heating system: a pump pushes the same water out through supply pipes and back through return pipes, rather than using it up.
How we know
His book De Motu Cordis (Frankfurt, 1628), his earlier lecture notes, and experiments others could repeat; the arm-tourniquet demonstration is still taught. Malpighi's 1661 capillaries completed the proof.
Still unknown or debated
Whether Harvey knew of Ibn al-Nafis's 13th-century account of lung circulation is unknown; he credited the Italian Realdo Colombo for that part.
Connections (4)
▸Galen was overturned by Harvey's discovery of blood circulationWell documented
The connection
Galen taught that the liver turned food into blood, which flowed outward and was consumed by the body, some seeping through tiny pores in the heart's wall. Harvey's measurements showed the heart pumps far too much blood for that to work, so blood must circulate. His proof overturned Galen's model of the blood after about 1,400 years.
When and how
Galen wrote in Rome around AD 160–200; Harvey, royal physician to James I and then Charles I, published De Motu Cordis in Frankfurt in 1628.
How we know
Harvey's book argues directly against Galen's model, and his measurements and tourniquet experiments could be repeated by anyone; most physicians accepted circulation within about 30 years.
Debates and open questions
Harvey kept other ancient ideas, such as the blood's vital spirit; historians debate whether he saw himself as overthrowing Galen or correcting him.
▸Ibn al-Nafis and the lung circulation anticipated part of Harvey's discovery of blood circulationWell documented
The connection
Ibn al-Nafis, a physician in Cairo, argued in 1242 that blood cannot pass through the heart's thick middle wall, as Galen claimed, but must travel from the right side through the lungs to the left. That is the pulmonary, or lung, circuit: one half of the full circulation Harvey proved in 1628.
When and how
Cairo, in his commentary on Ibn Sina's Canon, written around 1242; similar ideas reappeared in Europe with Michael Servetus (1553) and Realdo Colombo (1559).
How we know
His manuscript, rediscovered in Berlin in 1924 by the Egyptian physician Muhyo Al-Deen Altawi, states the idea clearly; whether it reached Europe is uncertain.
Debates and open questions
Some historians suggest his ideas reached Padua through Andrea Alpago's 1547 Latin translations of some of his writings; others think Europeans rediscovered them independently.
▸Vesalius's De humani corporis fabrica paved the way for Harvey's discovery of blood circulationWell documented
The connection
Vesalius made Padua the center of anatomy and taught that the body itself was the authority. His successors there, Realdo Colombo, who described the lung circuit, and Fabricius, who described vein valves, carried this approach on. Harvey studied under Fabricius in Padua and used those valves as key evidence for circulation.
When and how
Padua, from Vesalius's teaching in the late 1530s and 1540s through Fabricius's book on vein valves in 1603; Harvey studied there from 1599 to 1602.
How we know
University records show Harvey's study under Fabricius, and De Motu Cordis cites Colombo and Fabricius's valves.
Debates and open questions
Vesalius doubted but never fully rejected Galen's heart pores; historians debate how much credit the Padua lineage, versus Harvey's own measurements, deserves.
▸Harvey's discovery of blood circulation was the basis for Blood types and transfusionMostly agreed
The connection
Once Harvey showed in 1628 that blood circulates in a loop, putting blood into a vein made sense. In the 1660s Richard Lower transfused blood between dogs, and Jean-Baptiste Denys gave lamb's blood to people, but deaths soon led France to ban the practice. Transfusion became safe only after Landsteiner found blood types in 1901.
When and how
Oxford and London, 1665–67 (Richard Lower); Paris, June 1667 (Jean-Baptiste Denys); Vienna, 1901 (Karl Landsteiner).
How sure are we?
Lower's and Denys's experiments were reported in the Royal Society's Philosophical Transactions, and they took circulation as their starting premise.
Debates and open questions
Some of Denys's patients survived, probably because they received little blood; one patient's death led to a murder trial in which Denys was cleared and the patient's wife was suspected.