Leonardo was reported to have worked in the medical school of the university of Pavia, south of Milan, alongside the professor of anatomy. He may have dissected 20 corpses in the winter of 1510 – 1511, and the resulting drawings are among his finest scientific work. Here he studies the mechanisms of the hand, beginning with the bones, adding the muscles of the palm and wrist, and then successively the first and second layers of flexor tendons.