272 OSTEOLOGY 



the posterior and larger one is triangular or oval, and articulates with the cuboid; 

 the rough, non-articular area serves for the attachment of an interosseous ligament. 

 The three facets for articulation with the three metatarsal bones are continuous 

 with one another; those for articulation with the second cuneiform and navicular 

 are also continuous, but that for articulation with the cuboid is usually separate. 

 The dorsal surface is of an oblong form, its postero-lateral angle being prolonged 

 backward. The plantar surface is a rounded margin, and serves for the attachment 

 of part of the tendon of the Tibialis posterior, part of the Flexor hallucis brevis, 

 and ligaments. 



Articulations. The third cuneiform articulates with six bones: the navicular, second cunei- 

 form, cuboid, and second, third, and fourth metatarsals. 



For 4th 



For navicular For 2nd cuneiform metataraal For cuboid 



For 2nd 



metatarsal 



For 3rd 



metatarsal 



FIG. 282. The left third cuneiform. Postero-medial FIG. 283. The third left cuneiform. Antero- 



view. lateral view. 



The Metatarsus. 



The metatarsus consists of five bones which are numbered from the medial 

 side (ossa metatarsalia I.-V.); each presents for examination a body and two 

 extremities. 



Common Characteristics of the Metatarsal Bones. The body is prismoid in 

 form, tapers gradually from the tarsal to the phalangeal extremity, and is curved 

 longitudinally, so as to be concave below, slightly convex above. The base or 

 posterior extremity is wedge-shaped, articulating proximally with the tarsal bones, 

 and by its sides with the contiguous metatarsal bones: its dorsal and plantar 

 surfaces are rough for the attachment of ligaments. The head or anterior extremity 

 presents a convex articular surface, oblong from above downward, and extend- 

 ing farther backward below than above. Its sides are flattened, and on each is a 

 depression, surmounted by a tubercle, for ligamentous attachment. Its plantar 

 surface is grooved antero-posteriorly for the passage of the Flexor tendons, and 

 marked on either side by an articular eminence continuous with the terminal 

 articular surface. 



Characteristics of the Individual Metatarsal Bones. The First Metatarsal 

 Bone (os metatarsale I; metatarsal bone of the great toe} (Fig. 284). The first 

 metatarsal bone is remarkable for its great thickness, and is the shortest of 

 the metatarsal bones. The body is strong, and of well-marked prismoid form. 

 The base presents, as a rule, no articular facets on its sides, but occasionally 

 on the lateral side there is an oval facet, by which it articulates with the second 

 metatarsal. Its proximal articular surface is of large size and kidney-shaped; its 

 circumference is grooved, for the tarsometatarsal ligaments, and medially gives 

 insertion to part of the tendon of the Tibialis anterior; its plantar angle presents 

 a rough oval prominence for the insertion of the tendon of the Peronseus longus. 

 The head is large; on its plantar surface are two grooved facets, on which glide 

 sesamoid bones; the facets are separated by a smooth elevation. 



