150 CARPO-METACARPAL ARTICULATIONS 



8. Articiuitions between the Carpal Bones. These are amphi-arthroaial 

 joints, with the exception of the conjoined head of the os magnum and 

 unciforrne, which is received into a cup formed by the scaphoid, semi- 

 lunar, and cuneiform bone, and constitutes an enarthrosis. The ligaments 

 are, 



Dorsal, Interosseous fibre-cartilage, 



Palmar, Anterior annular. 



The dorsal ligaments are ligamentous bands, that pass transversely and 

 longitudinally from bone to bone, upon the dorsal surface of the carpus. 



The palmar ligaments are fasciculi of the same kind, but stronger than 

 the dorsal, having the like disposition upon the palmar surface. 



The interosseous ligaments are fibro-cartilaginous lamellae situated be- 

 tween the adjoining bones in each range: in the upper range they close 

 the upper part of the spaces between the scaphoid, semilunar, and cunei- 

 form bones ; in the lower range they are stronger than in the upper, and 

 connect the os magnum on the one side to the unciforme, on the other to 

 the trapezoides, and leave intervals through which the synovial membrane 

 is continued to the bases of the metacarpal bones. 



The anterior annular ligament is a firm ligamentous band, which con- 

 nects the bones of the two sides of the carpus. It is attached by one ex- 

 tremity to the trapezium and scaphoid, and by the other to the unciform 

 process of the unciforme and the base of the pisiform bone, and forms an 

 arch over the anterior surface of the carpus, beneath which the tendons of 

 the long flexors and the median nerve pass into the palm of the hand. 



The articulation of the pisiform bone with the cuneiform, is provided 

 with a distinct synovial membrane, which is protected by fasciculi of liga- 

 mentous fibres, forming a kind of capsule around the joint ; they are in- 

 serted into the cuneiforme, unciforme, and base of the metacarpal bone of 

 the little finger. 



Synovial Membranes. There nrefive synovial membranes entering into 

 the composition of the articulations of the carpus : 



The first is situated between the lower end of the ulna and the interar- 

 ticular fibro-cartilage ; it is called sacciform^ from forming a sacculus be- 

 tween the lateral articulation of the ulna with the radius. 



The second is situated between the lower surface of the radius and in- 

 terarticular fibro-cartilage above, and the first range of bones of the carpus 

 below. 



The third is the most extensive of the synovial membranes of the wrist ; 

 it is situated between the two rows of carpal bones, and passes between 

 the bones of the second range, to invest the carpal extremities of the four 

 metacarpal bones of the fingers. 



The fourth is the synovial membrane of the articulation of the meta- 

 carpal bone of the thumb with the trapezium. 



The jifth is situated between the pisiform and cuneiform bone. 



Actions. Very little movement exists between the bones in each range, 

 but more is permitted between the two ranges. The motions in the latter 

 situation are those of flexion and extension. 



9. The Carpo-metacarpal Articulations. The second row of bones of 

 the carpus articulates with the metacarpal bones of the four fingers by 

 dorsal and palmar ligaments; and the metacarpal bone of the thumb with 

 trie trapezium by a true capsular ligament. There is also in the carpo- 



