The =ulna= is massive. It is much longer and considerably heavier than the radius. The shaft is curved. The anterior surface is convex and most of it is rough and attached to the radius by the interosseous ligament. There is a smooth area on the upper third, which concurs with the radius in forming the upper interosseous space, and is marked in its upper part by the nutrient foramen. From this space a vascular furrow passes downward to the lower part of the shaft, where there is often a distal interosseous space for the passage of vessels. The internal surface is extensive, concave, and smooth. The external surface is slightly convex, and its upper part is marked by an oblique rough line or ridge. The proximal extremity is large and is bent inward somewhat; its length is more than one-third of that of the entire bone. The distal extremity is relatively small; it articulates with the ulnar and accessory carpal bones, and is notched in front to accommodate the ridge on the radius. The bone contains a considerable medullary canal. The bone is consolidated at three to three and a half years. The =carpus= comprises eight bones, four in each row. The bones of the proximal row resemble those of the ox, with the exception of the accessory, which is more like that of the horse, but has no external groove. The first carpal is small, elongated from before backward, rounded, and articulates in front with the second carpal. The latter is high and narrow, and articulates with the second and third metacarpal bones below. The third carpal articulates with the radial and intermediate above, the third metacarpal bone below. The fourth is the largest bone of the row; it articulates with the intermediate and ulnar above, the fourth and fifth metacarpals below, and bears a tuberosity on its volar aspect. [Illustration: FIG. 113.—SKELETON OF FOREARM AND MANUS OF PIG, ANTERO-EXTERNAL VIEW. _a_, Radius; _b_, ulna; _c_, radial carpal; _d_, intermediate carpal; _e_, ulnar carpal; _f_, accessory carpal; _g_, first carpal; _h_, second carpal; _i_, third carpal; _k_, fourth carpal; _l-o_, second to fifth metacarpal bones; _p-s_, second to fifth digits; _1_, olecranon; _2_, beak of ulna (proc. anconeus); _3_, semilunar notch; _4_, styloid process of ulna; _5_, styloid process of radius; _6_, distal epiphyseal lines; _7_, first phalanx; _8_, second phalanx; _9_, third phalanx. (Ellenberger-Baum, Anat. d. Haustiere.) ] Four =metacarpal bones= are present. The first is absent, the third and fourth are large and carry the chief digits, while the second and fifth are much smaller and bear the accessory digits. Their proximal ends articulate with each other and with the carpus as indicated above. The bones are consolidated at about two years of age.