THE FOOT 249 



ward. It occupies the centre of the front row of the tarsus, between the middle 

 cuneiform internally, the cuboid externally, the scaphoid behind, and the third 

 metatarsal in front. It is distinguished from the internal cuneiform bone by its 

 more regular wedge-like shape and by the absence of the kidney-shaped articular 

 surface; from the middle cuneiform, by the absence of the L-shaped facet, and 

 by the two articular facets which are present on both its inner and outer surfaces. 

 It has six surfaces for examination. 



The anterior surface, triangular in form, articulates with the third metatarsal 

 bone. The posterior surface articulates with the most external facet of the scaphoid, 

 and is rough below for the attachment of ligamentous fibres. The internal 

 surface presents two articular facets, separated by a rough depression; the anterior 

 one, sometimes divided into two, articulates with the outer side of the base of 

 the second metatarsal bone; the posterior one skirts the posterior border and articu- 

 lates with the middle cuneiform; the rough depression between the two gives 

 attachment to an interosseous ligament. The external surface also presents two 

 articular facets, separated by a rough nonarticular surface; the anterior facet, 

 situated at the superior angle of the bone, is small, and articulates with the inner 

 side of the base of the fourth metatarsal; the posterior and larger one articulates 

 with the cuboid; the rough, nonarticular surface serves for the attachment of 



For Wi 

 For scaphoid For middle-cuneiform metatarsal For cuboid 



For 2nd 

 metatarsal 



For 3rd 

 metatarsal 



FIG. 200. The left external cuneiform. A. Postero-internal view. B. Antero-external view. 



an interosseous ligament. The three facets for articulation with the three meta- 

 tarsal bones are continuous with one another, and covered by a prolongation of 

 the same cartilage; the facets for articulation with the middle cuneiform and 

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

 separate. The dorsal surface is of an oblong square form, its posterior external 

 angle being prolonged backward. The plantar surface is an obtuse rounded 

 margin, and serves for the attachment of ligaments and a part of the tendon of. 

 the Tibialis posticus, and for part of the fibres of origin of the Flexor brevis hallucis. 



To ascertain to which side the bone belongs, hold it with the broad dorsal surface upward, 

 the prolonged edge backward; the separate articular facet for the cuboid will point to the proper 

 side. 



Articulations. With ..r bones the scaphoid, middle cuneiform, cuboid, and second, third, 

 and fourth metatarsal bones. 



Attachment of Muscles. To two part of the Tibialis posticus, and Flexor brevis hallucis. 



The number of tarsal bones may be reduced owing to congenital ankylosis which may occur 

 between the os calcis and cuboid, the os calcis and scaphoid, the os calcis and astragalus, or the 

 astragalus and scaphoid. 



The Metatarsal Bones (ossa metatarsalia). The metatarsal bones are five 

 in number, and are numbered one to five, in accordance with their position from 

 within outward; they are long bones, and present for examination a shaft and two 

 extremities. 



