THE CARPUS. 



311 



A vertical section near 

 tically a screw surface. 

 surface is the apex of 

 cuneiform articulates w 

 The pisiform [os 

 where the greater part 

 lar facet which joins th 



the outer end is concave, near the inner convex. It is prac- 



A small part of the inner side is non-articular. The inner 



the pyramid, a small knob for the lateral ligament. The 



ith three bones, — the semilunar, pisiform, and unciform. 



pisiforme] is a small rounded bone, rough everywhere except 



of one surface is occupied by a round, slightly concave articu- 



e palmar aspect of the cuneiform. The facet is at the proxi- 



FiG. 327. 



Fig. 328. 



Rough surface for an- 

 terior annular lig- 

 ament and flexor 

 carpi ulnaris 



Right pisiform, dorsal aspect. 



For cuneiform 



Right pisiform, palmar aspect. 



mal part of the dorsal surface, the bone projecting from it downward, forward, and 

 inward, lying in a plane anterior to that of the outer carpal bones. The pisiform 

 articulates with only one bone, — the cuneiform. 



The trapezium [os multangulum raajus] is distinguished by an isolated facet 

 on the distal surface for the metacarpal bone of the thumb. This surface is that of 

 a typical saddle-joint, concave from side to side where the borders are most raised ; 

 convex from before backward ; broadest transversely. The proximal surface is a 

 four-sided concavity for the scaphoid, separated by a ridge from the inner surface. 

 The inner surface is subdivided : the proximal portion, much the larger, is an 

 articular concavity for the trapezoid ; the distal portion is rough except for a facet 

 at the dorsum for a part of the side of the second metacarpal. The outer surface is 

 concave, receiving the lateral ligament. The dorsal surface is elongated from side 

 to side, slightly hollowed in the middle, with a variously developed tubercle on 



Fig. 329. 



Fig. 330. 



For first metacarpal 



For second 

 metacarpal 



For trapezoid 



Ridge 



Groove for 

 flexor carpi radialis 

 For scaphoid 



For second 

 scaphoid | metacarpal 



For trapezoid 



Right trapezium, palmar aspect. 



Ridge 

 Right trapezium, proximal and inner aspect. 



either side. On the palmar surface is a deep groove for the tendon of the flexor 

 carpi radialis. Just beside this is a prominent ridge at the junction with the external 

 surface for a part of the outer insertion of the palmar annular ligament. The trape- 

 zium articulates with/c'?<r bones, — the scaphoid, trapezoid, and first and second meta- 

 carpals. 



The trapezoid [os multangulum minus] is best recognized by the dorsal surface, 

 which is pointed distally where it projects into the second metacarpal. The outer 

 convex border against the trapezium is much longer than the inner against the os 

 magnum. The proximal border runs obliquely forward and inward. The small 

 pahnar stnface is irregularly quadrilateral. The proximal surface is a quadrilateral, 

 nearly plane, facet for the scaphoid, longer from dorsum to palm than transversely. 

 The distal surface, entering the base of the second metacarpal, is divided by a ridge 

 into two facets, concave from dorsum to palm, of which the inner is the longer. 

 The interiial surface, in the main concave, articulates with the body of the os mag- 

 num, but has a non-articular surface near the dorsum for an interosseous ligament. 

 The outer surface is mostly articular and slightly convex, joining the trapezium ; 



