84 BONES OF THE UPPER LIMB. 



ligament is stretched across the carpus between these prominences, so as to 

 form a canal for the transmission of the flexor tendons. 



The superior surfaces of the scaphoid, semilunar and cuneiform bones 

 form, when in apposition, a continuous convexity which corresponds with 

 the concavity presented by the radius and the interarticular cartilage, while 

 the pisiform bone is attached in front of the cuneiform, with which alone it 

 articulates. The line of articulation between the superior and inferior ranges 

 is concavo-convex from side to side, the trapezium, trapezoid and os magnum 

 bounding a cavity which lodges the external part of the scaphoid, and the 

 os magnum and unciform rising up in a convexity, which is received into a 

 hollow formed by the scaphoid, semilunar, and cuneiform bones. 



THE SCAPHOID BONE. 



The scaphoid, or navicular bone, the largest and most external of the 

 first row of carpal bones, is of a curved form, and lies with its longest axis 

 directed outwards and downwards. Its superior surface, convex and smooth 

 for articulation with the radius, is inclined backwards, so that the posterior 

 surface of the bone is not so deep as the anterior. The internal surface, 

 narrow from above downwards, articulates with the semilunar bone. The 

 outer extremity, rough superiorly for the attachment of ligaments, presents 

 inferiorly an articular convexity, which occupies the hollow formed by the 

 upper surfaces of the trapezium and trapezoid bones, and is continuous 

 with a large concave surface extending over the rest of the inferior aspect 

 of the bone, and articulating with the os magnum. The fore part of the 

 outer extremity of the scaphoid bone projects forwards, forming one of the 

 tubercles to which the anterior annular ligament is attached. The scaphoid 

 articulates with five bones, viz., the radius, the semilunar, trapezium, 

 trapezoid, and os magnum, 



THE SEMILTJNAR BONE. 



The semilunar, or lunate bone, irregularly cubic, is named from the 

 crescentic concavity from before backwards of its inferior surface, which 

 rests on the head of the os magnum, and frequently also by a bevelled edge 

 slightly on the uuciform bone. Its external surface is vertical, and articu- 

 lates with the scaphoid bone ; its internal surface looks downwards and 

 inwards, is much deeper and narrower than the external, and articulates 

 with the cuneiform. The convex superior surface, which articulates with 

 the radius, is inclined, like that of the scaphoid, more backwards than 

 forwards, and hence the anterior surface is deeper than the posterior. The 

 semiluuar articulates with five bones, viz., the radius, scaphoid, cuneiform, 

 os magnum, and unciform. 



THE CUNEIFORM BONE. 



The cuneiform, or pyramidal bone, is somewhat wedge-shaped, its internal 

 extremity, rough for ligaments, forming the blunt narrow end of the wedge. 

 Superiorly it presents an articular surface, which glides upon the triangular 

 cartilage interposed between it and the ulna ; externally it articulates with 

 the semilunar bone, and inferiorly with the unciform, by means of a surface 

 which is concavo-convex from without inwards. Its anterior surface is dis- 

 tinguished from the posterior by a smooth circular facet on its outer half, 

 which articulates with the pisiform bone. The cuneiform articulates with 

 three bones, viz., the semilunar, pisiform, and unciform. 



