Muscles take precedence of bones in animal movements, 29 Oblique spiral muscles necessary for spiral bones and joints, 31 The spiral movements of the spine transferred to the extremities, 33 The travelling surfaces of animals variously modified and adapted to the media on or in which they move, 34–36 PROGRESSION ON THE LAND. Walking of the Quadruped, Biped, etc., 37 Locomotion of the Horse, 39 Locomotion of the Ostrich, 45 Locomotion of Man, 51 PROGRESSION ON AND IN THE WATER. Swimming of the Fish, Whale, Porpoise, etc., 66 Swimming of the Seal, Sea-Bear, and Walrus, 74 Swimming of Man, 78 Swimming of the Turtle, Triton, Crocodile, etc., 89 Flight under water, 90 Difference between sub-aquatic and aërial flight, 92 Flight of the Flying-fish; the kite-like action of the wings, 98 PROGRESSION IN OR THROUGH THE AIR. The wing a lever of the third order, 103 Weight necessary to flight, 110 Weight contributes to horizontal flight, 112 Weight, momentum and power to a certain extent synonymous in flight, 114 Air-cells in insects and birds not necessary to flight, 115 How balancing is effected in flight, 118 Rapidity of wing movements partly accounted for, 120 The wing area variable and in excess, 124 The wing area decreases as the size and weight of the volant animal increases, 132 Wings, their form, etc. All wings screws, structurally and functionally, 136 The wing, during its action, reverses its planes, and describes a figure-of-8 track in space, 140 The wing, when advancing with the body, describes a looped and waved track, 143 The margins of the wing, thrown into opposite curves during extension and flexion, 146 The tip of the bat and bird’s wing describes an ellipse, 147 The wing capable of change of form in all its parts, 147 The wing during its vibration produces a cross pulsation, 148 Compound rotation of the wing, 149 The wing vibrates unequally with reference to a given line, 150