THE WRIST-JOINT. 



99 



The internal lateral ligament is longer and thicker than the 

 external. It is attached by one end to the styloid process of the 

 ulna, and by the other to the rough upper part of the pyramidal 

 bone. Some of the anterior fibres are continued to the pisiform bone. 



The anterior ligament (fig. 41, J ) springs from the radius, and is 

 inserted into the first row of carpal bones, except the pisiform on 

 the anterior surface. 



The posterior ligament (fig. 44, 1, p. 103) is membranous, like the 

 anterior, and its fibres are directed downwards and inwards from 

 the radius to the same three 

 carpal bones on the posterior 

 aspect. 



Dissection. To see the 

 form of the articular sur- 

 faces, the joint may be 

 opened by a transverse in- 

 cision through the posterior 

 ligament, near the bones of 

 the carpus. 



Articular surfaces. The 

 end of the radius, and the 

 fibre-cartilage (fig. 42, c) 

 uniting it with the ulna 

 form a shallow socket for 

 the reception of the carpal 

 bones ; and the surface of 

 the radius is divided by a FIG. 41. FRONT VIEW OF THE ARTICU- 

 LATIONS OF THE WRIST, AND CARPAL 



AND MBTACARPAL BONES (BOURGERY). 



internal 

 lateral, 



anterior and 



posterior 

 ligaments. 



Dissection. 



1. Anterior ligament of the wrist- joint. 



2. Capsule of the joint of the metacarpal 

 bone of the thumb with the trapezium. 



3. Pisiform bone, with its ligamentous 

 bands. 



4. Transverse bands uniting the bases 

 of the metacarpal bones. 



prominent line into an ex- 

 ternal triangular, and an 

 internal square impression. 

 The three carpal bones of 

 the first row constitute a 

 convex eminence, which is 

 received into the hollow 

 before mentioned in this 

 way : the scaphoid bone is 



opposite the external triangular mark of the radius ; the semilunar 

 bone touches the square impression and the greater part of the 

 triangular nbro-cartilage ; while the small articular surface of the 

 pyramidal bone is in contact with the apex of the nbro-cartilage 

 and the adjoining part of the capsule. 



The synovial membrane has the arrangement common to simple 

 joints. This joint communicates occasionally with the lower radio- 

 ulnar articulation by means of an aperture in the nbro-cartilage 

 between the two. 



Movements. The principal movements taking place in the radio- 

 carpal articulation are flexion and extension. Lateral motion occurs 

 only to a limited extent. 



Flexion and extension. In flexion the hand is moved forwards, 

 while the carpus glides on the radius from before backwards, and 



H 2 



of first row 

 of carpal 

 bones : 



opposed 

 surfaces. 



Synovial 

 sac. 



Kinds of 

 motion : 



flexion ; 



