_Locomotion of the Ostrich._--Birds have been divided by naturalists into eight orders:--the _Natatores_, or Swimming Birds; the _Grallatores_, or Wading Birds; the _Cursores_, or Running Birds; the _Scansores_, or Climbers; the _Rasores_, or Scrapers; the _Columbæ_, or Doves; the _Passeres_; and the _Raptores_, or Birds of Prey. The first five orders have been classified according to their habits and modes of progression. The _Natatores_ I shall consider when I come to speak of swimming as a form of locomotion, and as there is nothing in the movements of the wading, scraping, and climbing birds,[28] or in the _Passeres_[29] or _Raptores_, requiring special notice, I shall proceed at once to a consideration of the _Cursores_, the best examples of which are the ostrich, emu, cassowary, and apteryx. [28] The woodpeckers climb by the aid of the stiff feathers of their tails; the legs and tail forming a firm basis of support. [29] In this order there are certain birds--the sparrows and thrushes, for example--which advance by a series of vigorous leaps; the leaps being of an intermitting character. The ostrich is remarkable for the great length and development of its legs as compared with its wings (fig. 24). In this respect it is among birds what the kangaroo is among mammals. The ostrich attains an altitude of from six to eight feet, and is the largest living bird known. Its great height is due to its attenuated neck and legs. The latter are very powerful structures, and greatly resemble in their general conformation the posterior extremities of a thoroughbred horse or one of the larger deer--compare with fig. 4, p. 21. They are expressly made for speed. Thus the bones of the leg and foot are inclined very obliquely towards each other, the femur being inclined very obliquely to the ilium. As a consequence the angles made by the several bones of the legs are comparatively small; smaller in fact than in either the horse or deer. [Illustration: FIG. 24.--Skeleton of the Ostrich. Shows the powerful legs, small feet, and rudimentary wings of the bird; the obliquity at which the bones of the legs and wings are placed, and the comparatively small angles which any two bones make at their point of junction. _a_ Angle made by femur with ilium. _b_ Angle made by tibia and fibula with femur. _c_ Angle made by tarso-metatarsal bone with tibia and fibula. _d_ Angle made by bones of foot with tarso-metatarsal bone. _r_ Bones of wing inclined to each other at nearly right angles. Compare with fig. 4, p. 21, fig. 26, p. 55, and fig. 27, p. 59.--Adapted from Dallas.]