Banning consists of the same succession of motions as walking; but these motions are so accelerated that there is a period between two steps when the body is not sup. .ported on either leg; and this constitutes the essential difference between the two paces. It requires afar greater expenditure of muscular force than walking, and cannot be long maintained without considerable exhaustion. First-rate runners can accomplish a mile in a few seconds under four minutes and a half, and 10 m. in an hour. (Lovett in a match with Frost, which came off on Mar. 22, 1852, at Copenhagen Fields, ran 10 m. 250 yds. in 52;53', and Deerfoot ran 11 in. 740 yds. at Brompton in an hour). In quad rupeds there are various paces besides walking, which are known as trotting, cantering, and galloping; and as every one is familiar with the ordinary paces of the horse, we shall take that animal as our illustration. In trotting, the horse moves its legs in pairs diago nally. Thus, if the left fore and right bind-leg be raised, and advanced first, the right fore and left hind-leg will be raised the instant the others reach the.ground. In fact, in trotting, the first pair are actually raised before the other legs reach the ground, so that there is a minute interval when all four legs are raised above the ground at the same time. The velocity acquired by moving the legs in pairs (as in running), instead of con secutively (as in walking), depends upon the circumstance that in trotting each leg rests on the ground during a short time and swings during a long time, while in walking the swing occupies a short period, and the rest a comparatively long one. In cantering, the animal, after advancing the two fore-legs one after the 'other, brings forward the two bind-legs simultaneously; and when this movement is greatly urged, the fore-legs are raised together, as well as the bind-legs, and the pace then becomes the gallop.
In leaping, the horse raises the fore-legs from the ground, and propels the body upward and forward by the hind legs alone. This act in the horse is, however, mainly the result of education, and those animals that leap or spring upon their prey (as the members of the cat tribe) crouch before leaping, in order to throw the body forward with the greatest possible force, by first bending all the limbs, and then suddenly extending them. As the hind legs are, however, the essential agents in leaping, we observe that in those animals whose natural mode of prooTession is leaping—as frogs, hares, kangaroos, etc.—the hind legs are much longer, and more muscular than the fore-legs. Leaping is a common mode of progression in many short-legged birds (blackbirds, thrushes, finches, sparrows, etc.), in whicT) the step would be extremely short if performed by moving the legs alternately. There is also a large number of insects, such as grasshoppers, fleas, etc., whose of progression is by leaks; 'unlit is in-this clam of animals that the leaping. power is developed to its greatest extent. The common flea, for example, can leap 200 times its own length. While fleas, locusts, and grasshoppers leap by means of their long and strong hind legs, other insects, as the podaridce, or spring-tails, possess a forked tail, which they bend beneath the body, and which, when' suddenly extended, propels them to a considerable distance.
Climbing, is merely svalking on an inclined or vertical surface. It is usually plished by means of sharp nails or claws, as in the cat-tribe, the lizards, etc. In many birds, as the woodpeckers, parrots, etc., the toes are arranged in two divisions, so as to grasp branches in the manner of a hand. Bears and sloths use their arms for climbing, while monkeys use their hands, and in some cases their tails. It is only in a very feNN cases, as id the sloth,. that this is the ordinary method of progression.
The act of piing in the bird is accomplished by the simultaneous action of the two anterior limbs, the wings, much as leaping is by that of the two posterior limbs. See
FLYING: BIRDS. Many attempts have been made to estimate the velocity at which dif ferent birds can fly. Whether, as has been stated, the eider-duck can fly 90, and the hawk 150 m. in an hour, is very questionable; but it has been ascertained that carrier pigeons can accomplish from 38 to 42 m. in that time.
The hats are the only mammals which possess a true power of flight. For a descrip tion of their organs and mode of flight, we must refer to the article BAT, where will also be found a notice of the false claims of some other mammals, as the so-called flying squirrel, to the possession of true'flight. Similarly, the actions of the flying lizard and of the flying-fish are not true flight. In no class of animals is the mechanism of flight so perfect as in insects. The dragon-fly, for example, can outstrip the swallow; and can do more in the air than any bird, as it can fly backwards and sidelong, to right or left, as well as forward without turning.. The wings of insects, of which there may be either one or two pair, are analagous (as instruments of motion) to the feathered wings of birds, but are regarded as homologous to (or in their essential nature) branchite or organs. For details regarding the mechanism employed in their aerial progression by insects, see INSECTS.
Swimming is the mode of progression employed by most aquatic animals. It mainly differs from flying in this respect, that water being much more dense than air, and the body of the animal being nearly of the same weight as the water it displaces, very little effort is required to keep the animal from sinking, and hence almost the whole of the muscular force can be employed in progression. In fishes, the locomotive organs consist of the fins and tail, the latter being the great propelling organ. The swimming of a fish has been correctly compared to the motion of a boat propelled by a single oar or scull at the stern. in the same manner as a succession of strokes alternately right and left pro pels the boat straight forward, so the fish advances by striking alternately right and left with its tail, The caudal fin, in which the tail ends, is vertical in fishes, and is usually considerably forked, when there is great speed. The ventral fins are for the purpose of keeping the fish in its proper position, with the back upwards, as is shown by a NI ell known experiment of Borelli, who, after cutting off these fins, restored the living fish to the water, when it rolled from side to side like a drunken man. The air-bladder with which many fishes are provided, and which they can distend and contract at pleasure, facilitates their swimming by enabling them to modify their specific gravity. Most ter restial mammals, excepting man, swim at once the first time they find themselves in deep water. The reason of this is, that their limbs move in water precisely as they do on land, and no new action either as regards direction or order is required, as is the case with man, to enable them to swim. Those which frequent the water, as seals, otters, and beavers, have webbed feet like ducks and other palmiped birds, the toes being united by membranes, which, when expanded, act as paddles. A large number of invertebrate animals move chiefly by swimming. Thus lobsters move by means of a vertical motion of the tail, and many of the crabs by means of their posterior legs, which are fashioned • like oars. Many insects swim with their legs, which are fringed with hairs to give addi tional surface. The cuttlefish uses its long arms as oars, and darts through the water with extreme rapidity; while other mollusks erect sail-like organs, by which they are propelled along the surface of the water. SWIMMING, as a gymnastic exercise, is described in a separate article.
Notices of the more special modes of progression will be found under a variety of heads. See CRUSTACEA, SERPENTS, WORMS.