In summary it should be pointed out that although the skeletal frame-work from which muscles operate determines to a large extent the course and direction of these organs, it is not safe to assume that it can be dismissed from our thinking. There has been a strong tendency to restrict orthodontic considerations to the morphology of the bony face and to view such morphology as static. It can never be forgotten that the close relationships between bones and muscles have been developed by adaptation and that the chief characteristic of that relationship is an equilibrium that serves to conserve energy. The teeth and alveolar processes should be looked upon as passive though responsive victims of a continuous interplay of muscular forces, their positions dictated by the resultants of these forces. No wishful thinking about straight profiles or upright incisors, nor the most clever appliance manipulation, will serve to hold teeth in positions that are contrary to the dictates of their muscular environment. It is to be hoped that the future will find us more aware of the significance of these matters.