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magnum. The two proximal sides are nearly straight; one is formed bv 

 the dorsal margin of the articulation between the unciforme and the 

 lunare, the other by the more extensive one between the unciforme and 

 cuneiforme. The three distal surfaces are articulated with part of the 

 base of the third, fourth and fifth metacarpal bones. The palmar side of 

 the unciforme presents, as its most striking character, a wedge-shaped 

 process, convex on both sides, which is impacted in the interspace be- 

 tween the lunar and cuneiform bones : immediately below this process 

 the surface is excavated and then swells out into a rough tuberosity near 

 the margins of the articular surfaces, by which the unciforme is united 

 with the third metacarpal. This surface is divided from that for the os 

 magnum by a narrow rough channel. The six articular surfaces covering 

 the rest of the circumference of the bone are uninterruptedly continuous ; 

 so that the rough dorsal and palmar surfaces of the bone are connected 

 by a similar non-articular tract along the radial, instead of the ulnar 

 margin. 



428. The metacarpal bone of the pollex or innermost digit. 



This bone presents a very singular and anomalous figure in conse- 

 quence of a thick and short process which is sent off from the ulnar side 

 of its base, which gives it the appearance of being bent at a right angle. 

 By this form it acquires two distinct proximal articulations or points of 

 support ; one at its base, or in the nominal position, by which it joins 

 that process of the scaphoides which represents the trapezium ; the 

 other on the before-mentioned process, with its plane at right angles to 

 the basal articulation, and abutting upon the proximal end of the ad- 

 joining metacarpal. An oblong subangular eminence extends along the 

 dorsal surface of the first metacarpal ; a convex rough protuberance 

 projects from the palmar aspect of its base, and is divided from a smaller 

 protuberance beyond it by a deep transverse groove. The two articular 

 surfaces at the proximal end of the bone are quite flat : the distal arti- 

 cular surface is a simple elliptical smooth convexity, occupying little 

 more than the ulnar half of the distal end of the bone : two small 

 smooth angular surfaces at the lower end of the articulation indicate the 

 sesamoid bones at the palmar aspect of this joint of the thumb. 



l 2 



