264 THE ARTICULATIONS. 



pisiform to the unciform, the piso-uncinate, and to the base of the fifth metacarpal 

 bone, the piso-metacarpal ligament (Fig. 174). 



2. ARTICULATIONS OF THE SECOND Row OF CARPAL BONES. 



These are also arthrodial joints. The articular surfaces are covered with carti- 

 lage, and connected by the following ligaments : 



Dorsal. Palmar. 



Three Interosseous. 



The Dorsal Ligaments extend transversely from one bone to another on the 

 dorsal surface, connecting the trapezium with the trapezoid, the trapezoid with 

 the os magnum, and the os magnum with the unciform. 



The Palmar Ligaments have a similar arrangement on the palmar surface. 



The three Interosseous Ligaments, much thicker than those of the first row, 

 are placed one between the os magnum and the unciform, a second between the 

 os magnum and the trapezoid, and a third between the trapezium and trapezoid. 

 The first of these is much the strongest, and the third is sometimes wanting. 



3. ARTICULATIONS OF THE Two Rows OF CARPAL BONES WITH EACH OTHER. 



The joint between the scaphoid, semilunar, and cuneiform, and the second row 

 of the carpus, or the mid-carpal joint, is made up of three distinct portions ; in the 

 centre the head of the os magnum and the superior surface of the unciform 

 articulate with the deep, cup-shaped cavity formed by the scaphoid and semilunar 

 bones, and constitute a sort of ball-and-socket joint. On the outer side the 

 trapezium and trapezoid articulate with the scaphoid, and on the inner side the 

 unciform articulates with the cuneiform, forming gliding joints. 



The ligaments are 



Anterior or Palmar. External Lateral. 



Posterior or Dorsal. Internal Lateral. 



The Anterior or Palmar Ligaments consist of short fibres, which pass, for the 

 most part, from the palmar surface of the bones of the first row to the front of the 

 os magnum. 



The Posterior or Dorsal Ligaments consist of short, irregular bundles of fibres 

 passing between the bones of the first and second row on the dorsal surface of the 

 carpus. 



The Lateral Ligaments are very short : they are placed, one on the radial, the 

 other on the ulnar side of the carpus ; the former, the stronger and more distinct, 

 connecting the scaphoid and trapezium bones, the latter the cuneiform and unciform ; 

 they are continuous with the lateral ligaments of the wrist-joint. In addition to 

 these ligaments, a slender interosseous band sometimes connects the os magnum 

 and the scaphoid. 



The Synovial Membrane of the Carpus is very extensive : it passes from the 

 under surface of the scaphoid, semilunar, and cuneiform bones to the upper surface 

 of the bones of the second row, sending upward two prolongations between the 

 scaphoid and semilunar and the semilunar and cuneiform ; sending downward 

 three prolongations between the four bones of the second row, which are further 

 continued onward into the carpo-metacarpal joints of the four inner metacarpal 

 bones, and also for a short distance between the metacarpal bones. There is a 

 separate synovial membrane between the pisiform and cuneiform bones. 



Actions. The articulation of the hand and wrist, considered as a whole, is 

 divided into three parts: (1) the radius and the interarticular fibro-cartilage ; 

 (2) the meniscus, formed by the scaphoid, semilunar, and cuneiform, the pisiform 

 bone having no essential part in the movements of the hand ; (3) the hand proper, 

 the metacarpal bones with the four carpal bones on which they are supported viz. 

 the trapezium, trapezoid, os magnum, and unciform. These three elements form 



