The notes reveal that Leonardo was concerned with three of the mechanisms of the leg: the action of the Achilles tendon, the role of the patella (knee-cap), and the antagonistic or mutually opposed action of muscles on either side of the leg. A number of Leonardo’s anatomical drawings show elements of the body from front, back and side. In principle, such orthogonal views give complete spatial information, but they can leave the viewer with little feeling for the true three-dimensionality of the body. Here Leonardo turns the body through 180 degrees in eight views, to give a wonderfully concrete sense of the superficial muscles of the arm and shoulder.