Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (An Anatomical Exercise on the Motion of the Heart and Blood in Living Beings) is the best-known work of the physician William Harvey. The book was first published in 1628 and established the circulation of the blood. It is a landmark in the history of physiology. Just as important as its substance was its method. Harvey combined observations, experiments, measurements and hypotheses in extraordinary fashion to arrive at his doctrine. His work is a model of its kind. It had an immediate and far-reaching influence on Harvey's contemporaries; Thomas Hobbes said that Harvey was the only modern author whose doctrines were taught in his lifetime. In the De motu cordis, Harvey investigated the effect of ligatures on blood flow. The book also argued that blood was pumped around the body in a "double circulation", where after being returned to the heart, it is recirculated in a closed system to the lungs and back to the heart, where it is returned to the main circulation.