208 THE SUPERIOR EXTREMITY 



concavity formed by the distal surfaces of the triquetral and 

 lunate bones and the distal part of the medial surface 

 of the navicular bone ; and the convex distal surface of the 

 navicular bone is received into a concavity formed by the 

 proximal surfaces of the greater and lesser multangular 

 bones. The two opposed surfaces of the transverse part of 

 the joint are, therefore, concavo-convex from side to side, 

 and adapted one to the other (Figs. 97, 98). 



Movements at the Carpal Joints. The movements at the carpal joints 

 supplement those at the radio-carpal joint, and tend greatly to increase the 

 range of movement at the wrist. Between the individual bones of each row 

 the movement is of a gliding character, and very limited. At the trans- 

 verse intercarpal joint volar and dorsal movements (flexion and extension) 

 alone are allowed. 



By the multiplicity of joints in this part of the limb, strength and 

 elasticity are contributed to the wrist. 



The nerve supply of the radio-carpal and intercarpal joints is derived 

 from the median, ulnar, radial and musculo-cutaneous nerves. 



Dissection. The interosseous muscles should now be re- 

 moved from the metacarpal bones. At the same time the flexor 

 tendons and lumbrical muscles may be detached from the fingers. 

 The extensor tendons, however, should be left in position on the 

 dorsal surfaces of the metacarpo-phalangeal and interphalangeal 

 joints. The ligaments which connect the carpus and meta- 

 carpus, and those which pass between the bases of the medial 

 four metacarpal bones, should be cleaned and denned. 



ARTICULATIONES INTERMETACARPE^E (INTERMETACARPAL 

 JOINTS). 



The four metacarpal bones of the fingers articulate with 

 one another by their basal or proximal extremities, and are 

 united together by strong ligaments. The metacarpal bone 

 of the thumb stands aloof from its neighbours, and enjoys 

 a much greater freedom of movement. 



The ligaments which bind the medial four metacarpal bones 

 to each other are 



1. A series of volar and dorsal bands, which pass trans- 

 versely and connect their basal extremities. 



2. Three stout interosseous ligaments, which occupy the 

 intervals between the basal ends of the bones. 



3. The transverse ligaments of the heads, which connect the 

 heads or distal extremities of the bones (p. 192). This liga- 

 ment has been removed in the dissection of the interosseous 

 muscles. 



