2677. Standing is the position of a lever "in equilibrio," the creation of the proper centre of gravity.
2678. Walking or running is an exchange or alternation of the equilibrium, a combination of standing and creeping.
2679. Leaping or hopping is a flight with the feet.
2680. Climbing is an use of the feet as hands.
c. Alary Motion.
2681. Flying is lever-swimming in the air. It takes place by means of aerial branchiæ, namely, the wings in Insects, and by the thoracic extremities in Birds, which are also none other than animal branchiæ.
2682. Soaring is creeping in the air.
2683. Hovering is standing in the air.