T'LXA. CARPUS. 



83 



is attached. Placed near the upper third is a foramen for vessels, directed 

 upwards into the medullary cavity. The internal surface is smooth, 

 and somewhat excavated superiorly on the side of the olecranon, where 

 it gives attachment to the flexor profundus muscle, while inferiorly it is sub- 

 cutaneous. The posterior surface, more uneven, looks outwards and back- 

 wards ; an oblique ridge, descending from behind the small sigmoid cavity, 

 limits a superior triangular area, which extends over the outer side of the 

 olecranon and gives attachment to the anconeous muscle ; immediately below 

 the small sigmoid cavity is a short space looking directly outwards, to which 

 the supinator brevis is attached ; while the remaining and largest part of this 

 surface is slightly impressed by the extensor muscles. Of the three margins, 

 the anterior and posterior are rounded, and for the most part smooth ; the 

 external is sharp, and gives attachment to the interosseous ligament. 



The inferior extremity presents a rounded articular head ; and on the 

 internal aspect of the head a short cylindrical projection, the styloid process, 

 which descends in a line with the inner and posterior surface of the shaft, 

 and gives attachment to the internal lateral ligament of the wrist joint. The 

 head presents two aspects, of which one, flattened and circular in form, looks 

 towards the wrist joint ; whilst the other, narrow and cylindrical, looks out- 

 wards, and is received into the semilunar cavity in the contiguous border of 

 the radius. The head and the styloid process are separated posteriorly by 

 a groove, which is traversed by the tendon of the extensor carpi ulnaris ; 

 and inferiorly by a depression, into which the triangular fibro-cartilage 

 which intervenes between the ulna and the carpus is inserted. 



THE CARPUS. 



The carpus is composed of eight short bones, which are disposed in two 

 ranges, four in each range. Enumerated from the radial to the ulnar side, 

 the bones which constitute the first or superior range are named scaphoid, 

 semilunar, cuneiform, and pisiform ; those of the second or inferior range. 

 trapezium, trapezoid, os magnum, and unciform. 



Fig. 75. HALF-DIAGRAMMATIC VIEW OP 

 THE CARPUS AND PROXIMAL PARTS OF THE 

 METACARPAL BONES, FROM BEFORE, WITH 

 THE CARPAL BONES SLIGHTLY SEPARATED 

 TO SHOW THE FORM OF THEIR SURFACES 

 OF CONTACT WITH EACH OTHER. f 



p- 



1, scaphoid bone ; 2, semilunar, pre- 

 senting in this instance, as often occurs, a 

 small surface of articulation with the unci- 

 form bone ; 3, cuneiform or pyramidal ; 

 4, pisiform, laid upon the last ; 5, trape- 

 zium, the figure is placed upon the ridge, 

 to the inside of which is the groove for the 

 tendon of flexor carpi radialis ; 6, trapezoid 

 bone ; 7, os magnum, the figure is placed 

 on the tuberosity ; 8, unciform bone, the 



figure is placed on the unciform process. The metacarpal bones will be distinguished by 

 the first being articulated separately with the trapezium. The articulation of the os 

 magnum with the fourth metacarpal bone is represented somewhat too large. 



The dorsal surface of the carpus is convex, the palmar is concave from 

 side to side, the concavity being bounded by four prominences, one at the 

 outer and one at the inner extremity of each range. The anterior annular 



G 2 



