THE CARPUS 



161 



into two parts by a ridge running from before backward. The lateral part articulates with the 

 greater multangular, the medial with the lesser multangular. The volar surface, rough and con- 

 cave above, is elevated below into a prominent tubercle for the attachment of the transverse 

 carpal ligament and the abductor pollicis hrevis. The dorsal surface is narrow, being reduced 



Fig. 190. — The Left Xavicular. 



For lunate 

 For radius 



For ligament 



For greater multangular 



For lesser multangula 



For capitate 



Tuberosity 



to a groove running the whole length of the bone; it is rough and serves for the attachment 

 of the dorsal radio-carpal ligament. The medial surface is occupied by two articular facets, 

 of which the upper is crescentic in shape for the lunate bone, whilst the lower is deeph' concave 

 for the reception of the head of the capitate. The lateral surface is narrow and rough for the 

 attachment of the radial collateral ligament of the wTist-joint. 



Articulations. — With the radius above, greater and lesser multangular below, lunate and 

 capitate medially. 



The Lunate 



The lunate [os lunatum] or semilunar (fig. 191), placed in the middle of the 

 proximal row of the carpus, is markedly crescentic in outline. 



The superior surface is smooth and convex and articulates with the medial of the two facets 

 on the distal end of the radius. The inferior surface presents a deep concavity divided into two 

 parts by a line running from before backward. Of these, the lateral and larger articulates with 

 the capitate; the medial and smaller with the hamate. The volar surface is large and convex, 



Fig. 191. — The Left Luxate. 



For triquetral - 



For hamate i^ 

 . For capitate 



the dorsal surface narrow and flat, and both are rough for the attachment of ligaments. The 

 medial surface is marked by a smooth quadrilateral facet for the base of the triquetral. The 

 lateral surface forms a narrow crescentic articular surface for the lunate. 



Articulations. — With the radius above, capitate and hamate below, navicular laterally 

 and triquetral medially. 



The Triquetral 



The triquetral [os triquetrum] or cuneiform (fig. 192) is pyramidal in shape 

 and placed obliquel}', so that its base looks upward and laterally and the apex 

 downward and medially. 



Fig. 192. — The Left Triquetral. 



For hamate 



The superior surface presents laterally near the base a small, convex articular facet which 

 plays upon the articular disc interposed between it and the distal end of the ulna, and medially 

 a rough non-articular portion for ligaments. The inferior surface forms a large, triangular 

 undulating facet for articulation with the hamate. The volar surface can be readily recognised 

 by the conspicuous oval facet near the apex for the pisiform bone. The dorsal surface is rough 

 for the attachment of ligaments. The medial and lateral surfaces are represented by the base 

 and the apex of the pyramid. The base is marked by a flat quadrilateral facet for the lunate. 

 The apex forms the lowest part of the bone and is roughened for the attachment of the ulnar 

 collateral hgament of the wTist. 



Articulations. — With the pisiform in front, lunate laterally, hamate below, articular disc 

 above. 



