Who challenged Galen's theory of the circulatory system?
Ibn al-Nafis
Leonardo da Vinci
William Harvey
Andreas Vesalius
Answer
Galen's theory of the circulatory system remained unchallenged until around 1242 when Ibn al-Nafis published his book Sharh tashrih al-qanun li' Ibn Sina (Commentary on Anatomy in Avicenna's Canon), in which he reported his discovery of pulmonary circulation.
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