200 



THE SKELETON 



The fibular portion of the navicular is sometimes united to the cuboid and quite separate 

 from the rest of the navicular, the cuboid in such cases articulating with the talus. This con- 

 dition suggests the recognition of the fibular portion of the navicular as a distinct accessory 

 tarsal element, the cuboides secundarium, though it has not yet been observed as an inde- 

 pendent bone in the human foot. 



THE METATARSUS 



The metatarsus [ossa metatarsalia] consists of a series of five somewhat 

 cylindrical bones. Articulated with the tarsus behind, they extend forward, 

 nearly parallel with each other, to their anterior extremities, which articulate 

 with the toes, and are numbered according to their position from great toe to small 

 toe. Like the corresponding bones in the hand, each presents for examination a 

 three-sided shaft, a proximal extremity termed the base, and a distal extremity or 

 head. The shaft tapers gradually from the base to the head, and is slightly 

 curved longitudinally so as to be convex on the dorsal and concave on the plantar 

 aspect, 



A typical metatarsal bone. — The shaft [corpus] is compressed laterally and 

 presents for examination three borders and three surfaces. The two borders, dis- 

 tinguished as medial and lateral, are sharp and commence behind, one on each side 

 of the dorsal aspect of the tarsal extremity, and, gradually approaching in the 

 middle of the shaft, separate at the anterior end to terminate in the corresponding 



Fig. 245. — The First (Left) Metatarsal. 



Fibular 

 or 



lateral side 



For peroneus longus 

 Facet for second meta- 

 tarsal (occasional) 



tubercles. The inferior border is thick and rounded and extends from the under 

 aspect of the tarsal extremity to near the anterior end of the bone, where it bi- 

 furcates, the two divisions terminating in the articular eminences on the plantar 

 aspect of the head. Of the three surfaces, the dorsal is narrow in the middle and 

 wider at either end. It is directed upward and is in relation with the extensor 

 tendons. The medial and lateral surfaces, more extensive than the dorsal, 

 corresponding with the interosseous spaces, are separated above, but meet to- 

 gether at the inferior border; they afford origin to the interosseous muscles. The 

 base is wedge-shaped, articulating by its terminal surface with the tarsus, and on 

 each side with the adjacent metatarsal bones. The dorsal and plantar surfaces 

 are rough for the attachment of ligaments. The head presents a semicircular 

 articular surface for tlio base of the first phalanx, and on each side a depression, 

 surmounted by a tubercle, for the attachment of the lateral ligaments of the 

 metatarso-phalangeal joint. The inferior surface of the head is grooved for the 

 passage of the flexor tendons and is bounded by two eminences continuous with 

 the terminal articular surface. 



The several metatarsals possess distinctive characters by which they can be 

 readily recognised. 



