THE TARSUS 



197 



the tuberosity; the inferior (plantar) surface is irregular and rough for the attach- 

 ment of the inferior calcaneo-navicular ligament, and the lateral surface is rough 

 and sometimes presents a small articular surface for the cuboid. 



Articulations. — With the talus behind, with the three cuneiform bones in 

 front, and occasionally with the cuboid on its lateral aspect. 



Ossification. — -The nucleus for the navicular appears in the course of the fourtli year. The 

 tuberosity of the navicular, into which the tibialis posterior acquires its main insertion, occasion- 

 all}' develops separateh", and sometimes remains distinct from the rest of the bone. 



The Cuneiform Bones 



Of the three cuneiform bones, the first is the largest, the second is the smallest, 

 and the third intermediate in size. They are wedge-shaped bones placed between 

 the navicular and the first, second and third metatarsal bones. Posteriorly, the 

 ends of the bones lie in the same transverse line, but in front, the first and third 

 project farther forward than the second, and form the sides of a deep recess into 

 which the base of the second metatarsal bone is received. 



Fig. 236. — The Left First Cuneiform. (Medial surface.) 



For first metatarsal 



Facet for the tendon of the tibialis 

 anterior 



The first cuneiform [os cuneiforme primum] (figs. 236, 237) is distinguished by its large 

 size and by the fact that when articulated, the base of the wedge is directed downward and the 

 apex upward. The posterior surface is concave and pyriform for articulation with the medial 

 facet on the anterior surface of the navicular. The anterior surface forms a reniform articular 

 facet for the base of the first metatarsal. The medial surface is rough, and pre.sents an oblique 

 groove for the tendon of the tibialis anterior; this groove is limited inferiorly by an oval facet 

 into which a portion of the tendon is inserted. The lateral surface is concave and presents along 

 its superior and posterior borders a reversed L-shaped facet for articulation with the second 

 cuneiform, and, at its anterior extremity, with the second metatarsal. Anteriorly it is rough 

 for ligaments. The inferior surface is rough for the insertion of the peroneus longus, tibialis 

 anterior, and (usually) the tibialis posterior. The superior surface is the narrow part of the 

 wedge and is directed upward. 



Fig 237. — The Left First Cuneiform. (Lateral aspect.) 



For second metatarsal 



For second cuneiform 



For navicular 



Articulations. — With the navicular behind, second cuneiform and second metatarsal on 

 its lateral side, and first metatarsal in front. 



Ossification. — From a single nucleus which appears in the course of the third year. 



The second cuneiform [os cuneiforme secundum] (figs. 238, 239) is placed with the broad 

 extremity upward and the narrow end downward, and is readily recognised by its nearly 

 square base. The posterior surface, triangular and concave, articulates with the middle facet 

 on the anterior surface of the navicular. The anterior surface, also triangular, but narrower 

 than the posterior surface, articulates with the base of the second metatarsal. The medial 

 surface has a reversed L-shaped facet running along its superior and posterior margins for 

 articulation with the corresponding facet on the first cuneiform, and is rough elsewhere for the 



