CARPUS. 221 



between the scaphoid and cuneiform. The superior surf ace, convex, smooth, and 

 bounded by four edges, articulates with the radius. The 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. The 

 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 articula- 

 tion with the scaphoid. The internal surface is marked by a smooth, quadri- 

 lateral 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 by its having an oval, 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, nonarticular 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. The posterior or dorsal surface is rough, for the attachments of liga- 

 ments. The anterior or palmar surface presents, at its inner side, an oval facet, 

 for articulation with the pisiform ; and is rough externally, for ligamentous 

 attachment. The external surface, the base of the pyramid, is marked by a flat, 

 quadrilateral, smooth facet, for articulation with the semilunar. The internal 

 surface, the summit of the pyramid, is pointed and roughened, for the attach- 

 ment of the internal lateral ligament of the wrist. 



To ascertain to which hand this bone belongs, hold it so that the base is 

 directed backwards, and the articular facet for the pisiform bone upwards ; the 

 concave articular facet will point to the side to which the bone belongs. 



Articulations. With three bones : the semilunar externally, the pisiform in 

 front, the unciform below, and with the triangular interarticular fibro-cartilage 

 which separates it from the lower end of the ulna. 



The Pisiform bone may be known by its small size, and by its presenting a 

 single articular facet. It is situated at the anterior and inner side of the carpus, 

 is nearly circular in form, and presents on its posterior surface a smooth oval 

 facet, for articulation with the cuneiform bone. This facet approaches the 

 superior, but not the inferior, border of the bone. The anterior or palmar 

 surface is rounded and rough, and gives attachment to the anterior annular 

 ligament. The outer and inner surfaces are also rough, the former being convex, 

 the latter usually concave. 



To ascertain to which hand it belongs, hold the bone with its posterior or 

 articular facet downwards, and the nonarticular portion of the same surface 

 backwards ; the inner concave surface will then point to the side to which the 

 bone belongs. 



Articulations. With one bone, the cuneiform. 



Attachment of Muscles. To two: the Flexor Carpi Ulnaris, and Abductor 

 Minimi Digiti ; and to the anterior annular ligament. 



BONES OF THE LOWER Eow. (Figs. 161, 162.) 



The Trapezium is of very irregular form. It may be distinguished by a deep 

 groove, for the tendon of the Flexor Carpi Radialis muscle. It is situated at 

 the external and inferior part of the carpus, between the scaphoid and first 

 metacarpal bone. The superior surface, concave and smooth, is directed upwards 



