146 



Bones of the Lower Extremity. 



I'll al an x III 



Tuberositas 

 unguicularis 



Phalanx II 



_ _Trochlea 

 _ Corpus 



Basis 



Trochlea 



Phalanx 1 



Capitulum 



Os metatarsale 



Corpus 



Basis 



197. Metatarsal bone and 

 phalanges of the third toe 

 of the right side, os meta- 

 tarsale II et phalanges digiti secundi, 



from the plantar aspect. 



(The arrows indicate the direction of the canales 

 nutricii.) 



The five ossa metatarsalia (metatarsal 



bones) (see also Figs. 198203) are short cylin- 

 drical bones in which can be distinguished a shaft 

 or corpus , a proximal end, basis , and a distal 

 end, capitulum. On the whole they are curved 

 so as to be somewhat convex dorsalward. 



The corpus is triangularly prismatic so that 

 one side looks dorsalward, the other two lateral- 

 and medianward; the latter meet in the border 

 directed plantarward. A foramen nutricium 

 situated plantarward corresponds to the one in 

 the hand (see p. 109). 



The basis is somewhat broadened, supports 

 on its proximal side an articular surface for con- 

 nection with the tarsus aud from the second to 

 the fifth toe also small articular surfaces at the 

 sides for the neighboring metatarsal bones. The 

 basis ossis metatarsalis I possesses a large con- 

 cave, bean -shaped articular surface (for the os 

 cuneiforme I), but no lateral articular surfaces; 

 on the plantar surface a blunt nodule, luberosilas 

 ossis metatarsalis 1, projects lateralward (see 

 Fig. 201). Projecting from the side of the basis 

 ossis metatarsalis V backward is a strong pro- 

 cess, the tuber ositas ossis metatarsalis V (see 

 Figs. 198, 200 and 201). 



The capitulum is flattened laterally, pos- 

 sesses a spherical articular surface, covered with 

 cartilage, which extends further upon the plantar 

 than upon the dorsal surface. At the sides are 

 rough areas for the articular ligaments. 



The four spaces between the ossa metatar- 

 salia, spatia interossea metatarsi, (see Figs. 200 

 and 201) correspond to the spatia interos: ja meta- 

 carpi (see page 109.) 



The phalanges digitorum correspond in 

 number, arrangement and form as well as in the 

 relations of their foramina nutricia entirely to 

 those of the hand (see p. 109), except that they 

 are all essentially shorter. The 2 " d and 3 rd phalanx 

 of the 5 th toe are often ankylosed. 



As to ossa sesamoidea (sesamoid bones) 

 (see Fig. 201), two are constantly found at the 

 metatarsophalangeal joint of the great toe, a third 

 less constant, at the interphalangeal joint of the 

 same toe; a fourth is situated in the tendon of 

 the m. peronaeus longus in front of the lateral 

 angle of the tuberositas ossis cuboidei and a fifth 

 sometimes in the tendon of the m. tibialis poste- 

 rior below the fibrocartilago navicularis. 



