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15. Os Metacarpi Magnus, Metacarpal or Cannon Bone.—The large metacarpal, or cannon bone, is a long, straight bone, placed in a vertical direction. Its superior or upper extremity articulates with the carpus and its inferior or lower extremity articulates with the os suffraginis and the two sesamoids.

16. Ossa Metacarpi Parva, or Splint Bones.—The two small metacarpal, or splint bones, tuberous in form (marked or covered with projections) at the carpus and tapering distally (lower portion), are attached to the large bone, one on each side of its posterior (back) surface, by ligaments in the young animal, and by ossification (union of bone) in most grown up, and in all old animals.

17. Proximal Phalanx, Os Suffraginis, or Large Pastern Bone.—The os suffraginis, or large pastern bone, passes obliquely downwards and forwards, and articulates with the cannon bone above, and the median phalanx or os coronae below. It belongs to the class of long bones.

18. Great Sesamoid Bones.—These bones, two in number, are placed side by side at the postero-inferior (back and lower) part of the metacarpus and postero-superior (back and upper) part of the os suffraginis; they are irregular in shape, their back parts are covered with cartilage, for the passage of the flexor tendons of the digit or the last four bones of the limb. Their superior or upper surface is roughened, and their sides, which are grooved for the reception of the suspensory ligament. (This is called the fetlock joint.)