Giovanni Alfonso Borelli is remembered today chiefly as the author of the posthumously published work, De motu animalium.1 This is understandable, because we have there a work of great importance in which the movement of living creatures is interpreted, fully and systematically, from a strictly mechanical point of view, and in which the locomotory apparatus of animals-at least, of vertebrates, for Borelli was concerned only with them-is regarded as an assembly of connecting-rods and levers.