In the fourth order the scratchers (_Rasores_), to which the common fowl, the pheasant, and the pigeon belong, the foot is adapted for an instrument of active locomotion, as well as for the purpose of procuring food by scratching in the earth. Hence we find it strong, with a long muscular leg, and four toes, three before and one behind, covered with broad scales and armed with short claws. The thumb, so necessary for perching and climbing, is in birds of this order short, rudimentary, and attached high up in the leg, so that the whole foot being placed flat upon the ground, affords a very firm support to the animal. In the fifth order of birds, the runners (_Cursores_), to which the ostrich, the emu, and the cassowary belong, the structure of the foot is wholly that of a powerful instrument of locomotion. The leg is long, the thigh strong and muscular, and the foot short and compact. The toes which never exceed two or three in number, and of which the second is the largest, are placed all in front, and armed with very short claws, or, as in the African ostrich, with the outer toe destitute of a claw. The scales are limited to the upper surface of the foot, the under surface being flexible and occupied by an elastic pad upon which the member rests. Such a conformation of limb, which would be wholly useless for perching or climbing, is admirably fitted for running—witness the swiftness of the ostrich—a creature equalling and even surpassing the fleetest horse in speed. In the sixth order, the waders (_Grallatores_), or stilt birds, as the stork, the crane, the heron, &c., the leg is long and slender, and the foot weak and covered with shield-shaped scales. The toes, four in number, are long and straight, three being placed anteriorly, and a shorter one (wanting in the plovers and lapwings) behind; they are frequently palmated at their base, as in the stork; or, as in the middle claw of the heron, toothed or notched like a saw; while sometimes they have a narrow-winged appendage, running along the side, as in the sandpipers. In search of their food, insects and small fish, the individuals of this order frequent marshy places and shallow waters, and many of them, as the stork and heron, are remarkable for the unerring certainty with which they strike and seize their small finny prey. In the last order, the swimmers (_Natatores_), called also web-footed birds, to which the goose, duck, and gull belong, the foot is modified to assist in swimming. The legs are short; the four toes, all placed in front, are united by a broad membranous expansion, and armed with claws, the thumb being likewise brought in front, so that a greater extent of surface may be given to this oar-like member. A foot thus constructed would be wholly unsuited for perching, running, or grasping, but it is well adapted to the wants and habits of these aquatic birds.