THOEACIC LIMBS 619 



metacarpal respectively. The metacarpus presents two surfaces, the 

 dorsal and the palmar, and two ends, the proximal, or upper, and 

 the distal, or lower. 



The dorsal surface is slightly convex from above downward, and 

 decidedly convex from side to side ; this convexity is much more 

 evident on the radial, or thumb, side. 



The palmar surface is concave from the radial to the ulnar side, 

 and also slightly from the proximal to the distal end. 



The proximal end is irregular, and is higher on the radial than on 

 the ulnar side. 



The distal end presents the form of a truncated triangle, inasmuch 

 as the third and fourth metacarpals are longer than the second and fifth. 



The constituent bones of the metacarpus are nearly parallel ; they 

 are contiguous at their upper ends and bound together by strong liga- 

 ments, but free below for the rest of their length. Inasmuch as the 

 lower ends are wider than the shafts, spaces are left between the shafts, 

 the so-called interosseous spaces, which are filled in part by inter- 

 osseous muscles. The metacarpal of the thumb, the length whereof 

 is only about one-third the length of the metacarpal of the index, is 

 in a different plane from the others, so that its dorsal surface faces 

 almost directly toward the radial side. 



Nomenclature. The term metacarpus is the Latin translation of 

 the Greek metacarpion of Galen, a compound of meta, beyond, and 

 carpion, the carpus. The old Latin name was pecten manus, because 

 the separate bones looked like the teeth of a comb. It is known in 

 German as die Mittelhand, and in French as le metacarpe. 



CHARACTERS COMMON TO ALL METACARPAL BONES. 



General Description. Every metacarpal consists of a proximal 

 extremity, or base, a central part, or shaft, and a distal extremity, 

 or head. 



The metacarpal of the thumb differs so decidedly from the rest 

 that it must be described separately. The following explanation 

 applies, therefore, only to the other four. 



The Base is irregularly cuboidal in shape, and is not divided from 

 the shaft by a conspicuous neck. In every metacarpal it presents 

 individual peculiarities in shape and in the arrangement of its promi- 

 nences and depressions. 



