CARPUS. 141 



the dorsal surface being generally the broadest of the two. The superior and 

 inferior 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. Their structure in all is similar, con- 

 sisting within of cancellous tissue inclosed in a layer of compact bone. Each 

 bone is also developed from a single centre of ossification. 



BONES OF THE UPPER Row. (Figs. 94 and 95.) 



The Scaphoid is the largest bone of the first row. It has received its name 

 from its fancied resemblance to a boat, being broad at one end, and narrowed like 

 a prow at the opposite. It is situated at the upper and outer part of the carpus, 

 its direction being from above downwards, outwards, and forwards. Its superior 

 surface is convex, smooth, of triangular shape, and articulates with the lower end 

 of the radius. Its inferior surface, directed downwards, outwards, and backwards, 

 is smooth, convex, and triangular, and divided by a slight ridge into two parts, 

 the external of which articulates with the trapezium, the inner with the trapezoid. 

 Its posterior or dorsal surface presents a narrow, rough groove, which runs the 

 entire breadth 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 tubercle, which projects forwards from the front 

 of the carpus, and gives attachment to the anterior annular ligament of the wrist. 

 The external surface is rough and narrow, and gives attachment to the external 

 lateral ligament of the wrist. The internal surface presents two articular facets : 

 of these the superior or smaller one is flattened, of semilunar form, and articulates 

 with the semilunar bone; the inferior or larger is concave, forming, with the 

 semilunar bone, a concavity for the head of the os magnum. 



To ascertain to which hand this bone belongs, hold the convex radial articular 

 surface upwards, and the dorsal surface backwards ; the prominent tubercle will 

 be directed to the side to which the bone belongs. 



Articulations. With five bones ; the radius above, trapezium and trapezoid 

 below, os magnum and semilunar internally. 



The Semilunar bone may be distinguished by its deep concavity and crescentic 

 outline. It is situated in the centre of the upper range of the carpus, between 

 the scaphoid and cuneiform. Its superior surface, convex, smooth, and quadrilateral 

 in form, articulates with the radius. Its inferior surface is deeply concave, and 

 of greater extent from before backwards, than transversely ; it articulates with the 

 head of the os magnum, and by a long narrow facet, separated by a ridge from 

 the general surface, with the unciform bone. Its anterior or palmar and posterior 

 or dorsal surfaces are rough, for the attachment of ligaments, the former being the 

 broader, and of somewhat rounded form. The external surface presents a narrow, 

 flattened, semilunar facet, for articulation with the scaphoid. The internal surface 

 is marked by a smooth, quadrilateral facet, for articulation with the cuneiform. 



To ascertain to which hand this bone belongs, hold it with the dorsal surface 

 upwards, and the convex articular surface backwards ; the quadrilateral articular 

 facet will then point to the side to which the bone belongs. 



Articulations. With five bones : the radius above, os magnum and unciform 

 below, scaphoid and cuneiform on either side. 



The Cuneiform (TOs Pyramidal) may be distinguished by its pyramidal shape, 

 and from having an oval-shaped, isolated facet, for articulation with the pisiform 

 bone. It is situated at the upper and inner side of the carpus. The superior 

 surface presents an internal, rough, non-articular portion; and an external or 

 articular portion, which is convex, smooth, and separated from the lower end of 

 the ulna by the interarticular fibro-cartilage of the wrist. The inferior surface, 

 directed outwards, is concave, sinuously curved, and smooth, for articulation with 

 the unciform. Its posterior or dorsal surface is rough, for the attachment of liga- 

 ments. Its anterior or palmar surface presents, at its inner side, an oval-shaped 



