THE RADIO-CARPAL 



235 



pollicis to the back of the semilunar and cuneiform bones; and (iii) from the 

 groove for the radial extensors to the back of the scaphoid and semilunar. It is 

 in relation with, and strengthened V)y, the extensor tendons which pass over it. 



The internal lateral ligament (fig. 232) is fan-shaped, with its apex above, at 

 the styloid process of the ulna, to which it is attached on all sides, blending witli 

 the apex of the fibro-cartilage. Some of the fibres pass forwards and outwards to 

 the base of the i)isiform bone and to the inner part of the upper border of th(^ 

 anterior annular ligament, where it is attached to the pisiform bone; they form a 

 thick, rounded fasciculus on the front of the wrist. Other filjres descend verti- 

 cally to the inner side of the cuneiform bone, and others again outwards to the 

 dorsal surface of the cuneiform. The tendon of the extensor carpi nlnarh is pos- 

 terior to, and passes over, part of the fibres of the ligament. 



The external lateral ligament (fig. 231) consists of fibres which radiate from 

 the fore part and tip of the styloid process of the radius. Some pass downwards 

 and inwards, in front, to the scaphoid and adjacent edge of the magnum; some 

 downwards, a little forwards and inwards, to the tubercle of the scaphoid and ridge 



Fig. 232. — Postekiue View of Wkist. 



Posterior radio-earpa] 

 ligament 



Capsule of earpo-meta- 

 carpal joint of thumb 



Posterior radio- 

 ulnar ligament 



Internal lateral 

 ligament of wrist 





of the trapezium ; and others downwards and outwards to the rough dorsal surface 

 of the sca})lioid. The filn'es of this ligament are not so long and strong, nor do 

 they radiate so much as those of the internal lateral ligament. It is in relation 

 with the radial artery, and the extensor ossis metacarpi and primi internodii pollicis, 

 the artery separating the tendons from the ligament. 



The synovial membrane is extensive, but does not usually communicate with 

 the synovial membrane of the inferior radio-ulnar joint, being shut out by tlie 

 triangular (cartilage. It is also excluded, in almost every instance, from that of the 

 carpal joints by the interosseous ligaments between the first row of carpal bones. 

 The styloid process of the radius is cartilage-covered internalh", and forms part of 

 the articular cavity, while that of the ulna does not. 



The arterial supply is derived from the anterior and posterior carpal arches, the 

 ])osterior division of the anterior interosseous, from twigs direct from the radial and 

 ulnar arteries, and from recurrent branches from the first dorsal interosseous. 



The nerve-supply is derived from the ulnar and median in front, and the pos- 

 terior interosseous behind. 



Movements. — The wrist is a condyloid joint, the carpus forming the condyle. 

 It allows of movements upon a transverse axis, i.e. flexion and extension; and 



