3IO 



HUMAN ANATOMY. 



articular : the upper, very narrow, articulates at its lower border with the semilunar 

 and gives attachment above to the fibro-cartilaginous ligament connecting these 

 bones ; the lower is an elongated cavity embracing part of the top and the outer 

 side of the head of the os magnum. The outer siirface, continuous with the dorsum, 

 is a small groove for the lateral ligarnent of the wrist. The distal surface, forming 

 the convexity of the medio-carpal joint, articulates with the trapezium and trapezoid. 

 It is convex in all directions. The scaphoid articulates withy?z^^ bones, — the radius, 

 semilunar, trapezium, trapezoid, and os magnum. 



The semilunar [os lunatum] receives its name from its outline when seen from 

 the side, the proximal surface being convex and the distal deeply concave. The 

 dorsal surface is quadrilateral. Its proximal and inner borders are longer than the 



Concavity for 

 magnum 



Fig. 323. 



Fig. 324. 



For cuneiform For unciform 



Dorsal 



For radius 



magnum 



For scaphoid 

 Right semilunar, outer aspect. 



Palmar 

 Right semilunar, inner aspect. 



others, so as to make it kite-shaped, the long axis running distally outward. The 

 two shorter surfaces meet at an overhanging point. The palmar surface is of the 

 same general shape. Its larger distal portion is smooth as for a bursa. T\\& proxi- 

 mal surface is convex and articular, chiefly for the radius ; but, extending under the 

 triangular cartilage, broadest at the scaphoid edge, it narrows internally. The con^ 

 cave distal surface is divided by a ridge into a larger part for the os magnum and an 

  inner for the edge of the unciform. An outer surface articulates with the scaphoid 

 and an i^iner with the cuneiform. Both are semilunar, but the outer is the more 

 slender. Both are nearly plane and practically wholly articular, there being but a 

 slight roughness for the interosseous ligaments at the proximal end near the dorsum. 

 The semilunar articulates with five bones, — the radius, scaphoid, cuneiform, o» 

 magnum, and unciform. 



The cuneiform [os triquetrum], or pyramidal, is of such form that the latter 

 name is the more fitting. The base is the articular surface for the semilunar ; the 

 apex is at the inner side of the wrist. The base is plane and articular except where 

 the interosseous ligament joins it. The dorsal surface is narrow and not clearly 



For pisiform 



Fig. 325. 



For unciform 



For semilunar 



Lateral 

 ligament 



Palmar surface 



For triangular cartilage 

 Right Luneiform, palmar aspect. 



Fig. 326. 



For unciform 



Dorsal surface 

 For semilunar 



Non-articular 

 Right cuneiform, distal aspect. 



separated from the proximal on the macerated bone. The proximal surface is a 

 triangle with the base inward, and has near the base a smaller triangle of" articular 

 surface for the triangular cartilage. The inner half of the palmar stirface is occupied 

 by a round facet for the pisiform. The distal surface is a very complexly curved 

 articular facet for the unciform. It suggests a saddle-joint that has been spirally 

 twisted. A transverse section of this surface is concavo-convex from withQut inward. 



