The skull (Fig. 154, p. 306) is long, especially the facial portion, the eye-socket (orbit) being shifted behind the teeth, which otherwise, on account of their great height, would press upon the eye itself; the orbit is completely encircled in bone. The lower jaw is deep vertically and the ascending ramus (see p. 66) very high, on account of the hypsodont character of the teeth, which thus necessitates a remodelling of the skull in several respects. The neck is long, each of its seven vertebræ being elongate; except in the atlas and axis, the anterior face of each centrum is strongly convex and the posterior of all except the atlas is deeply concave; the odontoid process of the axis (see p. 71) is spout-shaped, concave on the upper and convex on the lower side, lodging and protecting the spinal cord. The spines of the anterior dorsal vertebræ are very high, making a low hump at the withers between the shoulder-blades; the trunk-vertebræ are so arranged as to make the back almost straight and horizontal. The limbs and especially the feet are very long. The two bones of the fore-arm, the ulna and radius, are coössified into a single piece (Fig. 30, p. 81), but the limits of each are still plainly to be seen, especially in a young animal; and it is evident that the ulna is greatly reduced in size and has lost its middle portion, while all the weight is borne by the radius. Similarly, in the hind leg the enlarged tibia, or shin-bone, alone supports the weight; and only the two ends of the fibula are preserved (Fig. 38, p. 87), and these are indistinguishably fused with the tibia in the adult animal, but may be made out in the colt. The thigh-bone has a very characteristic shape, which is difficult to describe without an undue use of technical terms, but the unusual prominence of the great trochanter (Fig. 35, p. 85) and of the rotular groove is an important factor in producing this appearance. [Illustration: FIG. 148.—Left pes of Horse. _Cal._, calcaneum. _As._, astragalus. _N._, navicular. _Cn. 3_, third cuneiform. _Mt. III_, functional (third) metatarsal. _Mt. II_ and _Mt. IV_, splints.] [Illustration: FIG. 149.—Left manus of Horse, front side; to the right, rear view of the metacarpus. _S._, scaphoid. _L._, lunar. _Py._, pyramidal. _Pis._, pisiform. _Td._, trapezoid. _M._, magnum. _U._, unciform. _Mc. II_, _Mc. IV_, rudimentary second and fourth metacarpals, or splints.]