196 



SPECIAL ANATOMY OF THE SKELETON 



Common Characters of the Carpal Bones. Each bone (excepting the pisi- 

 form) presents six surfaces. Of these the anterior, palmar, or volar, and the 

 posterior or dorsal are rough for ligamentous attachment, the dorsal surface being 

 the broader, except in the scaphoid and semilunar. The superior or proximal 

 and inferior or distal are articular, the superior generally convex, the inferior 

 concave; and the internal and external are also articular when in contact with 

 contiguous bones, otherwise rough and tubercular. The structure of all is similar, 

 consisting of cancellous tissue enclosed in a layer of compact bone. Each bone 

 is also developed from a single centre of ossification. 



1 Pisiform 



/ -- ~-<s 



FIG. 152. Diagram to show articulations. 



Bones of the Upper Row. The scaphoid or navicular bone (os naviculare 

 manus} (Fig. 153) is the largest bone of the first row. It is situated at the upper 

 and outer part of the carpus, its long axis being from above downward, outward, 

 and forward. 



For radius 



For semilwnar 



Tuberosity 



For os 

 For trapezoid 



A B 



FIG. 153. The left scaphoid. A, seen from behind; B, seen from in front. 



Surfaces. The superior surface is convex, smooth, of triangular shape, and 

 articulates with the lower end of the radius. The inferior surface, directed down- 

 ward, outward, and backward, is smooth, convex, also triangular, and divided by 

 a slight ridge into two parts, the external of which articulates with the trapezium, 

 the inner with the trapezoid. The posterior or dorsal surface presents a narrow, 

 rough groove which runs the entire length of the bone and serves for the attachment 

 of ligaments. The anterior or palmar surface is concave above, and elevated at 

 its lower and outer part into a prominent rounded tuberosity (tuberculum ossis 

 navicularis), which projects forward from the front of the carpus and gives attach- 



