Jean Pecquet (9 May 1622, Dieppe, Seine-Maritime – 26 February 1674) was a French scientist. He studied the expansion of air, wrote on psychology, and is also known for investigating the thoracic duct. Furthermore, he studied the nature of vision.
He studied medicine at Montpelier, where he made the important discovery of the course of the lacteal vessels, including the receptaculum chyli, or reservoir of Pecquet, as it is sometimes called, and the termination of the principal lacteal vessel, the thoracic duct, into the left subclavian vein. He dissected the eye and measured its dimensions. Contrary to Edme Mariotte, he maintained that the retina, not the choroid, was the principal organ of vision. He wrote:
Experimenta Nova Anatomica (Paris, 1651; English translation, as New Anatomical Experiments, 1653)