86 ELEMENTS OF MAMMALIAN ANATOMY. 



The entocuneijorm is next to the smallest bone of the 

 tarsus. It articulates with the navicular, mesocuneiform, 

 and first and second metatarsals. The mesocuneiform is 

 a wedge-shaped bone and the smallest element of the 

 tarsus. It articulates with the other two cuneiforms, 

 the navicular and second metatarsal. The ectocuneiform 

 may be recognized by a strong hook-like process on its 

 plantar surface. It articulates with the navicular, meso- 

 cuneiform, cuboid, and second and third metatarsals. 



The cuboid is the lateral bone of the distal row. It 

 may be recognized by the deep groove on its plantar 

 surface which shelters the tendon of the peroneus longus 

 muscle. 



The typical arrangement of the tarsal elements in ver- 

 tebrates is similar to that of the carpus. Three bones, 

 a tibiale, intermedium, and fibulare, compose the proximal 

 row, while five tarsalia form the distal row. The centrale 

 occupies the center of the tarsal region. In the adult 

 mammal fusion of some of these elements occurs, so that 

 not more than seven distinct bones are present in any 

 form. The astragalus contains the tibiale and inter- 

 medium, while the fourth and fifth tarsalia form the 

 cuboid. 



The metatarsus consists of five bones, the first of which 

 is rudimentary, while the other four are longer than the 

 metacarpus, which they resemble (Fig. 43). The first 

 metatarsal is smaller than any bone of the tarsus. It 

 articulates with the entocuneiform and is also in contact 

 with the second metatarsal. The four long metatarsals 

 have a slight dorsal convexity, each one consisting of a 

 base or enlarged proximal part, a shaft or middle portion, 

 and a head or distal rounded articular process. On the 

 plantar surface of the head of each metatarsal is a median 

 spine, on each side of which is a concavity for a sesamoid 



