94 



BONES OF THE UPPER LIMB. 



area, bounded by lines -winch, proceedinfij from the sides of the head, 

 pass upwards and converge in the second, third, and fourth metacarpal 

 bones opposite the middle of the carpal extremity, and in the fifth 

 towards its inner side. 



The heads or digital exfremifies 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 pre- 

 sent hollows and elevations for the attachment of ligaments. 



The carpal extremity presents distinctive peculiarities in each meta- 

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

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

 with tlie trapezium ; and posteriorly a rough prominence, to which the 

 extensor ossis 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 out- 

 wards, and externally with the fourth metacarpal bone, while on its 

 ulnar side it presents a rough and prominent tuberosity. 



Fig. 80. From the proximal position of its epi- 



physis, the metacariial 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 

 l)halanx of the middle row.^^v*,^v. \(i-j»j- U 



Fig. so. — Right Hand seen froj: behind. 

 (A. T.) i 



The indications are the same as in the pre- 

 ceding figure. 



THE DiaiTAL PHAX.ANGES. 



The digital phalanges, or inter nodia, 

 are fourteen in number ; three for each 

 finger, except the-.lhumb, which has 

 only two. 



Those of the first row are slightly 

 curved like the metacarpal bones. 

 Their dorsal surfaces are smooth and 

 transversely convex ; the palmar are 

 fiat from side to side, and bounded by 

 rough margins, which give insertion to 

 the fibrous sheaths of the flexor tendons. Their proximal extremities 

 are thick, and articulate each by a transversely oval concave surface with 

 the corresponding metacarpal bone. Their distal extremities, smaller and 



