METACABPAL BONES AND PHALANGES. 



87 



present on their dorsal surfaces each a triangular subcutaneous area, bounded 

 by lines which, proceeding from the sides of the head, pass upwards and con- 

 verge in the second, third, and fourth metacarpal bones opposite the middle 

 of the carpal extremity, aud in the fifth towards its inner side. 



The heads or digital extremities articulate with the proximal phalanges. 

 Their smooth rounded surfaces are broader, and extend further on the 

 palmar than on the dorsal aspect of the bones; and on the sides present 

 hollows and elevations for the attachment of ligaments. 



The carpal extremity presents distinctive peculiarities in each metacarpal 

 bone. That of the first has only one articular surface, concave from 

 before backwards, and convex from side to side, which articulates with the 

 trapezium; and posteriorly a rough prominence, to which the extensor 

 metacarpi pollicis is attached. The second presents a transversely concave 

 surface which receives the trapezoid bone ; on the radial side it articulates 

 by a small facet on its posterior part with the trapezium, on the ulnar side 

 with the third metacarpal bone, and by a narrow facet wedged between the 

 third metacarpal and trapezoid bones, with the os magnum. The third 

 bone articulates superiorly with the os magnum, and on the sides with the 

 contiguous metacarpal bones : at its posterior and outer angle it forms a 

 projection upwards. The fourth articulates principally with the unciform 

 bone above, but also by a narrow facet with the os magnum ; on its radial 

 side are two small surfaces, and on the ulnar side one, for articulation with 

 the adjacent metacarpal bones. The fifth articulates superiorly with the 

 unciform bone by means of a concave surface inclined slightly outwards, and 

 externally with the fourth metacarpal bone, while on its ulnar side it 

 presents a rough and prominent tuberosity. 



From the proximal position of its epiphysis, the metacarpal bone of the thumb 

 has been considered by Winslow and some other anatomists, as a phalanx of the first 

 row, and the bone which it supports a phalanx of the middle row. 



THE DIGITAL PHALANGES. 



Fig. 78. RIGHT HAND SEEN FROM BEHIND. | 



The indications are the same as in the pre- 

 ceding figure. 



The digital phalanges, or inter nodia, 

 are fourteen in number; three for each 

 finger, except the thumb, which has 

 only two. In each instance the first or 

 proximal phalanx is longer than the 

 second, and the second longer than the 

 third. 



Those of the first row are slightly 

 curved like the metacarpal bones. 

 Their dorsal surfaces are smooth and 

 transversely convex; the palmar are 

 flat from side to side, and bounded by 

 rough margins, which give insertion to 

 the fibrous sheaths of the flexor ten- 

 dons. Their proximal extremities are 

 thick, and articulate each by a trans- 

 versely oval concave surface with the 

 corresponding metacarpal bone. Their distal extremities, smaller and more 



