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Jean Riolan, William Harvey and the Circulatory System

In 1628 William Harvey (1578 to 1657) published his theory of the circulation of the blood in his Exercitatio anatomica de motu cordis et sanguinis in animalibus (Frankfurt). He was obliged to further extend his ideas in response to criticisms, particularly in his public correspondence with Jean Riolan (c.1577 to 1657).

Harvey's lecture notes from Padua show that by 1616 he accepted the theory of Realdo Colombo that the active movement of the heart was its systole (contraction), and that blood travelled from the heart to the lungs where it mixed with air. This was opposed to the Galenic tradition in which blood passed through the ventricles of the heart, with air being supplied by the pulmonary vein, and moved into the arteries as the heart passively contracted, following its forcible diastole (expansion).

In Exercitatio anatomica de motu cordis he outlined the idea of the active systole and pulse, before then going on to discuss the evidence pointing to the circulatory system, arguing that the heart pumped the blood into the arteries, then passed into the veins and returned to the heart.

Harvey also calculated the quantity of blood pumped by the heart, which he claimed was not consumed by the body, but circulated in a closed system to all parts so that all parts of the body may be nourished, warmed, and activated by the hotter, perfect , vaporous, spirituous, and so to speak, nutritious blood. The worn out blood was then returned to the heart where the blood was restored to its erstwhile state of perfection.

His method of developing knowledge was based on research and experiment and he argued his case based on the results of vivisection and dissection. He used the same process in Exercitationes de generatione animalium (1651), the result of more than twenty years of experimentation, dissection and logic.

The reaction to his 1628 work was mixed. Descartes and Riolan, while not disputing the idea of circulation, disagreed on several points and both produced alternative theories of circulation.

In his Encheiridium anatomicum et pathalogicum (1648) and his Opuscula anatomica nova (1649) Riolan reacted to Harvey 's discoveries. Riolan objected to Harvey's theories on the grounds that it undermined Galen and his theoretical basis of the practice of medicine. He also mistrusted the assumption that the anatomy of animals may be comparable to humans and strongly disapproved of vivisection. He maintained there was more of an ebb and flow of blood through the veins, that it returned to the heart no more than a few times a day, and that it was consumed by the body. He also disagreed with Harvey's assertion that the heart drove the circulation of the blood, preferring that the blood kept the heart in motion, analogous to a waterwheel. In his theory of circulation, Riolan preserved the Galenic physiology, with three hierarchic spheres of the body, with separate blood circulation.

Riolan was the only critic to whom Harvey responded, in his Two Anatomical Essays on the Circulation of the Blood, and argued that Riolan's reluctance to accept his theories stemmed from his fear of destroying traditional medicine. In his response to these essays Riolan demonstrates his respect for Harvey, claiming that he was happy and fortunate to have got such a censor.

Descartes was more in agreement with Riolan than Harvey, accepting the full circulation of blood around the body, but arguing that the pulse of the heart was caused by the alternate vaporising and condensing of blood.

By Harvey's death in 1657, the theory of circulation had established a relative consensus and it was widely accepted, at least by scholars, by the late 1660s.

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