The drawing depicts the inside of the left leg, with the calf muscles prominent and many of the tendons, nerves and vessels visible. To upper right is a discussion of the action of standing on the ball of the foot. In the note alongside Leonardo describes the relaxing calf muscle as literally ‘deflating’, as it was believed that ‘pneuma’, systemic air coursing through the body, was responsible for the swelling, hardening and contraction of muscles. Above is an oblique view of the sole of the foot, with the plantar aponeurosis (the tough connective tissue that supports the arch of the foot) removed to reveal the nerves and first layer of muscles. Below, the nerves and several muscles have been removed to show the tendons more clearly. The interpenetration of the tendons towards the toes parallels the arrangement in the fingers that so impressed Leonardo in his studies of the hand, and he thus noted that ‘the hand is to the arm as the foot is to the leg’.