Derived from two popular lectures, the author examines the anatomy and mechanics of the lower and upper extremities, showing how concentrated locomotive function in the legs enables upright posture and frees the hand for manipulation. He traces the principle of division of labour through comparative examples from simple animals to humans, outlines the bones, joints, arches and ligaments of the foot (including the distinctive role of the great toe), and discusses elastic properties, structural homologues in other species, and the coordinated role of muscles and nervous control in support and locomotion. Clear anatomical comparisons illuminate form and function.