CARPO-METACARPAL AND INTERMETACARPAL ARTICULATIONS. 175 



which extends from the prominences made by the trapezium and scaphoid bone on 

 the radial side of the carpus, directly across to the pisiform bone and unciform pro- 

 cess, and converts the transverse arch of the carpus into a ring through which the 

 flexor tendons of the digits pass into the hand. 



The posterior annular ligament, placed at the back of the wrist, is only a 

 thickened part of the aponeurosis of the forearm. It extends from the lower part of 

 the radius, at its outer border, to the inner part of the pyramidal and pisiform bones, 

 and serves to bind down the extensor tendons. 



THE CARPO-METACARPAL AND INTERMETACARPAL ARTICULATIONS. 



The four inner metacarpal bones are bound together at their distal extre- 

 mities by fibres passing between the palmar ligaments of the metacarpo-phalangeal 

 articulations, and constituting the transverse metacarpal Ligament. At their proximal 



Fig. 202. GENERAL VIEW OP THE ARTICULATIONS OP THE 



WRIST AND HAND FROM BEFORE. 



1, lower part of the interosseous membrane ; 2, and from 

 that point across the lower end of the radius, the anterior 

 radio-carpal ligament ; 3, scaphoid bone ; 4, pisiform ; 5, tra- 

 pezium ; 6, unciform ; 7, os magnum, with most of the deeper 

 ligaments uniting these bones ; I, first metacarpo-phalangeal 

 articulation with its external lateral ligament ; II to V, trans- 

 verse metacarpal ligament ; in the several interphalangeal arti- 

 culations of the fingers the lateral ligaments are shown ; in the 

 thumb the external only is visible. 



extremities they are united to one another and to 

 the carpal bones in articulations, the common syno- 

 vial lining of which is derived from that of the 

 intercarpal joint. In these articulations the four 

 metacarpal bones are bound together by three 

 dorsal, and three palmar, and by strong interos- 

 seous ligaments. The second, third and fourth 

 metacarpal bones are united to the carpus by dorsal 

 ligaments, of which each bone receives two, viz., the 

 second from the trapezium and trapezoid, the third 

 from the trapezoid and os magnum, and the fourth 

 from the os magnum and unciform, and by palmar 

 ligaments, one to each bone, but which are not so 

 well defined and less constant. The fifth metacarpal bone is united to the unciform 

 bone by a thin capsule which surrounds the articulation except on the outer side. 

 There is likewise an interosseous band in one part of the carpo-metacarpal articula- 

 tion, connecting the lower and contiguous angles of the os magnum and unciform to 

 the adjacent angle of the third metacarpal bone. This ligament sometimes sepa- 

 rates the cavity between the unciform and two inner metacarpal bones^from the rest 

 of the joint. 



The first metacarpal bone is articulated with the trapezium by a capsular 

 investment, which is thickened behind and on the outer side, and is lined by a dis- 

 tinct sy no vial membrane. 



