224 THE SKELETON. 



Attachment of Muscles. Part of the Flexor Brevis Pollicis. 



The Unciform bone may be readily distinguished by its wedge-shaped form, 

 and the hook-like process that projects from its palmar surface. It is situated 

 at the inner and lower angle of the carpus, with its base downwards, resting 

 on the two inner metacarpal bones, and its apex directed upwards and out- 

 wards. The superior surface, the apex of the wedge, is narrow, convex, smooth, 

 and articulates with the semilunar. The inferior surface articulates with the 

 fourth and fifth metacarpal bones, the concave surface for each being separated 

 by a ridge, which runs from before backwards. The posterior or dorsal surface 

 is triangular and rough, for ligamentous attachment. The anterior or palmar 

 surface presents, at its lower and inner side, a curved hook-like process of bone, 

 the unciform process, directed from the palmar surface forwards and outwards. 

 It gives attachment, by its apex, to the annular ligament ; by its inner surface, 

 to the Flexor Brevis Minimi Digiti, and the Flexor Ossis Metacarpi Minimi 

 Digiti ; and is grooved on its outer side, for the passage of the flexor tendons 

 into the palm of the hand. This is one of the four eminences on the front of 

 the carpus, to which the anterior annular ligament is attached ; the others being 

 the pisiform internally, the oblique ridge of the trapezium and the tuberosity 

 of the scaphoid externally. The internal surface articulates with the cuneiform 

 by an oblong surface, cut obliquely from above, downwards and inwards. The 

 external surface articulates with the os magnum by its upper and posterior part, 

 the remaining portion being rough, for the attachment of ligaments. 



To ascertain to which hand it belongs, hold the apex of the bone upwards, 

 and the broad dorsal surface backwards : the concavity of the unciform process 

 will be directed to the side to which the bone belongs. 



Articulations. With five bcnes : the semilunar above, the fourth and fifth 

 metacarpal below, the cuneiform internally, the os magnum externally. 



Attachment of Muscles. To two: the Flexor Brevis Minimi Digiti, the Flexor 

 Ossis Metacarpi Minimi Digiti ; and to the anterior annular ligament. 



THE METACARPUS. 



The Metacarpal "Bones are five in number ; they are long cylindrical bones, 

 presenting for examination a shaft, and two extremities. 



Common Characters of the Metacarpal Bones. The shaft is prismoid in form, 

 and curved longitudinally, so as to be convex in the longitudinal direction 

 behind, concave in front. It presents three surfaces : two lateral, and one pos- 

 terior. The lateral surfaces are concave, for the attachment of the Interossei 

 muscles, and separated from one another by a prominent line. The posterior or 

 dorsal surface is triangular, smooth, and flattened below, and covered, in the 

 recent state, by the tendons of the -extensor muscles. In its upper half it is 

 divided by a ridge into two narrow lateral depressions, for the attachment of 

 the Dorsal Interossei muscles. This ridge bifurcates a little above the centre 

 of the bone, and its branches run to the small tubercles on each side of the 

 digital extremity. 



The carpal extremity, or base, is of a cuboidal form, and broader behind than 

 in front : it articulates above with the carpus, and on each side with the adjoin- 

 ing metacarpal bones; its dorsal and palmar surf aces being rough, for the attach- 

 ment of tendons and ligaments. 



The digital extremity, or head, presents an oblong surface, flattened at each 

 side, for articulation with the first phalanx ; it is broader, and extends farther 

 forwards in front than behind, and is longer in the antero-posterior than in the 

 transverse diameter. On either side of the head is a deep depression, sur- 

 mounted by a tubercle, for the attachment of the lateral ligament of the meta- 

 carpo-phalangeal joint. The posterior surface, broad and flat, supports the ex- 

 tensor tendons; the anterior surface presents a median groove, bounded on each 

 side by a tubercle, for the passage of the flexor tendons. 



