Jean Riolan the Younger (February 15, 1577 - February 19, 1657) was a French anatomist who was an influential member of the Medical Faculty of Paris. He is remembered for his traditional views towards medicine, and was a major proponent of the teachings of Galen. He held a differing viewpoint in regards to William Harvey's theory involving the blood's circulatory system. Riolan calculated that blood traveled through the blood vessels to the body's extremities and returned to the heart only two or three times a day. He also postulated that blood often ebbed and flowed in the veins and that it was taken in as nourishment by different parts of the body. He also did not believe that the heart propelled the blood, instead he proposed that the blood kept the heart in motion, analogous to a stream moving the wheel of a water mill. Riolan was an opponent to the practice of vivisection, asserting that violent and painful deaths suffered by research animals, placed them in an unnatural condition that led to incorrect assumptions about the functionality of healthy animals. His best known written works are Anthropographie (1618), which is a treatise on human anatomy, and Opuscula anatomica (1649), in which he is critical of Harvey's views of the circulatory system. He died in 1657 at the age of 80.