89 



but is separated by a rough tract, half an inch broad, from the surface on the 

 opposite side of the lunare, for the os cuneiforme : the two remaining articular 

 surfaces which converge and meet at the lower angle of the lunare are adapted, 

 the one to the os magnum, the other to the unciforme. 



The OS cuneiforme or triquetrum (c) is the largest of the carpal bones and ap- 

 proaches to the cubical figure ; the rough quadrilateral dorsal surface is nearly 

 flat, with an oblong protuberance near the radial margin, and a concavity above 

 the edge of the lower articular surface. The upper or proximal end presents an 

 almost square flat articular surface for the truncated distal end of the ulna, 

 which surface bends over upon the outer and posterior surface of the bone, 

 to form the slightly convex semioval articulation for the os pisiforme. The 

 articular surface of the opposite side for the lunare is divided by a rough 

 tract from the ulnar surface, but is continuous with the broad and slightly 

 sinuous one by which the cuneiforme articulates with the unciform bone : on 

 the outer or ulnar side of this surface, a small articular facet is marked off, by 

 which the cuneiform assists in supporting the huge metacarpal bone of the little 

 finger. Thus the proximal row of carpal bones is brought into contact with the 

 metacarpal series at both its extremities, and circumscribes, with this series, the 

 space including the three distinct bones of the second carpal row. 



These bones consist, as already stated, of the trapezoides, os magnum and un- 

 ciforme, and progressively increase in size in the or(^r in which they are enu- 

 merated. The trapezoides (e) resembles a patella in form, but has an articular 

 surface on its convex as well as concave side : its rough base is at the dorsal sur- 

 face of the carpus, subconvex, subtriangular, with the apex turned towards but 

 separated by an interspace from the trapezial process of the scaphoid. The proximal 

 articular surface connecting the trapezoides with the scaphoid proper is semi- 

 circular and slightly convex ; that which joins with the os magnum is a small, 

 circular, subconcave surface. The distal articular surface supporting the second 

 or index metacarpal is convex next the dorsal part of the carpus and concave 

 towards the palmar side, in the vertical direction, with opposite curvatures in 

 T* the transverse. 



The OS magnum (J) is wedged in between the scaphoides, lunare, trapezoides, 

 unciforme and middle metacarpal bone, and its rugged dorsal surface is bounded 

 by sides corresponding with each of these bones : of these the one connected 



M 



