DISSECTING MANUAL. 



ference of the head has a narrow convex facet for the radius. 

 The inferior surface of the head is flat, semilunar, and sepa- 

 rated from the styloid process by a groove. [197] 



Radius. The upper extremity has a disc-shaped head with a 

 concavity superiorly, for the capitellum; and a smooth cir- 

 cumference, broadest internally, for the small sigmoid cavity 

 and orbicular ligament. Below the head is a constriction 

 (neck); and below this, internally, an oval prominence (bicip- 

 ital tuberosity) which is rough posteriorly but smooth ante- 

 riorly. [199] 



The shaft is narrow above but broad below, triangular on 

 section with the base outward, and curved outward; it has 

 two surfaces separated by two borders. The internal (inter- 

 osseous) border descends from the posterior border of the bi- 

 cipital tuberosity, becoming sharper, and splits at the middle 

 third into two lines; these run to the ends of the sigmoid 

 cavity, enclosing a triangular area. The external border is 

 thick and rounded above, has a rough impression at its centre, 

 becomes sharper below, and ends in the styloid process. The 

 anterior (flexor) surface has a ridge (anterior oblique line) 

 running, from the bicipital tubercle, downward and outward to 

 the middle of the outer border. The posterior (extensor) sur- 

 face has a similar but less distinct ridge (posterior oblique 

 line) which also ends at the centre of the outer border. [200] 



The lower extremity is triangular and turned slightly for- 

 ward. Its lower surface is concave; a slight antero-posterior 

 ridge divides this into two facets, a triangular external one for 

 the scaphoid, and a quadrilateral inner one for the semilunar 

 bone. The anterior border is prominent and rough ; the pos- 

 terior is rough and has many grooves for tendons. A pointed 

 process (styloid) descends from the outer side; its outer sur- 

 face has a shallow groove. On the inner side of this extremity 

 is a narrow facet (sigmoid cavity) for the ulna; this is plane 

 vertically, concave transversely, and separated from the carpal 

 facets by a rectangular edge. [201] 



ruei 



