Cuboid. Os cuboideum ([Fig. 58], c).—The cuboid has somewhat the form of a cube and articulates by its proximal end with the calcaneus (a), and by its distal end with the fourth and fifth metatarsals. Its medial surface articulates with the scaphoid (d) and lateral cuneiform (e). The ventral surface is marked near its distal end by an oblique ridge, distad of which is a deep groove, the peroneal groove (h), for the tendon of the peroneus longus muscle.
Scaphoid. (Os naviculare pedis BNA) ([Fig. 58], d).—The scaphoid is a boat-shaped bone. Its proximal surface is marked by a concave facet for the head of the astragalus (b), and its distal surface has three facets for the lateral (e), intermediate and medial (g) cuneiform bones. At the junction of the ventral with the medial surface is a prominent tubercle. The lateral surface bears two linear facets for articulation with the calcaneus (a) and cuboid (c).
Lateral Cuneiform. Ectocuneiform. Os cuneiforme tertium BNA ([Fig. 58], e).—The lateral cuneiform is a wedge-shaped bone with a hooked process extending from the ventral sharp angle of the bone. It articulates by its proximal end with the scaphoid (d), and by its distal end with the third metatarsal. The medial surface bears near its distal end two facets for the second metatarsal, and on its proximal end a facet for the intermediate cuneiform. The caudal surface has a facet on its proximal end for the cuboid (c).
Intermediate Cuneiform. Mesocuneiform. Os cuneiforme secundum BNA.—The intermediate cuneiform is small and wedge-shaped, with the base of the wedge dorsad. It lies between the lateral cuneiform and the medial cuneiform, articulates by its proximal end with the middle facet of the scaphoid, and bears on its distal end the second metatarsal. It is not visible in ventral view.
Medial Cuneiform. Entocuneiform. Os cuneiforme primum BNA ([Fig. 58], g).—The medial cuneiform lies on the medial side of the foot. It is a flat triangular bone about twice as long as broad, and broader at its proximal end than at the distal end. It bears on its distal end the rudimentary first metatarsal. The proximal end is oblique and bears a concave facet for the lateral distal facet of the scaphoid (d). The lateral surface has a concave facet at its proximal end for the intermediate cuneiform, while the distal portion is applied against the medial surface of the second metatarsal.
Bones of the Foot or Pes
([Fig. 58]).—Metatarsals. Metatarsus ([Fig. 58], 1-5).—The metatarsals are five in number. They bear a close resemblance to the metacarpals, but they may be distinguished by their bases.
The first metacarpal (1) is rudimentary and conical. Its base has a facet for the distal end of the medial cuneiform (g), while the outer surface fits into a depression on the inner surface of the base of the second metatarsal.
The second (2). The proximal surface of the base is triangular, corresponding to the distal end of the intermediate cuneiform. The medial surface is marked by two concavities, one along the proximal border for the distal end of the medial cuneiform, and one distad of this for the first metatarsal. The lateral surface bears on the proximal margin an oblique triangular facet dorsad and a similar facet ventrad, both for the lateral cuneiform (e). Distad of these facets is a rough ridge.
The third (3). The proximal end of its base is a triangular facet with the apex directed ventrad and the sides excavated. It is for the distal end of the lateral cuneiform (e). Its medial surface presents a depression which receives the ridge of the second metatarsal. On the lateral surface a short distance distad of the proximal border is a triangular concave facet, and near the proximal border ventrad a second concave facet. Both are for the fourth metatarsal.