OSTEOLOGY. 55 



Flyloid process, projects from the posterior and internal part 

 of the extremity,, its apex gives attachment to the internal lateral 

 ligament of the wrist, and it is marked at its root by a depression 

 between it and the head, for attachment of the fibro-cartilage ; 



Groove, upon the posterior surface, for passage of extensor 

 carpi ulnaris. 



It articulates with two bones humerus and radius. 



Its muscular attachments are sixteen brachialis anticus, 

 triceps, anconeus, flexor and extensor carpi ulnaris, pronator radii 

 teres, flexor sublimus and profundus digitorum, pronator quad- 

 ratus, supinator brevis, extensor indicis, extensor ossis metacarpi, 

 extensor secundi internodii pollicis, and flexor longus pollicis. 



Its ossific centres are three one each for shaft, olecranon, 

 and inferior extremity. 



THE RADIUS is a long bone, shorter than the ulna, situated 

 on the outer side of the forearm, the upper end small, the shaft 

 slightly curved, and the lower end expanded to form part of the 

 wrist-joint. It consists of shaft, upper and lower extremity. 



The shaft is prismoid, slightly curved, and presents 



An internal border, sharp and prominent, for interosseous 

 membrane ; 



An anterior border, marked at its upper third by an oblique 

 line, for attachment of flexor longus pollicis, supinator brevis, 

 and flexor sublimis digitorum; 



Anterior surface, affords attachment above for flexor longus 

 pollicis, below for pronator quadratus, and presents at the junc- 

 tion of middle and upper two-thirds a nutrient foramen directed 

 upward ; 



Posterior surface gives attachment at upper third to supina- 

 tor brevis, and at middle third to extensors of thumb. 



The upper extremity presents: 



Head a cup-like cylindrical cavity, for articulation with 

 capltellum of humerus, and on its side an articulating surface 1 

 for lesser sigmoid cavity of ulna and orbicular ligament, which 

 nearly surrounds it ; 



Neck, the constricted portion below the head ; 



Bicipital tuberosity, below and to inner side, divided by a 

 vertical line into a rough surface posteriorly, for attachment of 

 biceps tendon, and smooth surface anteriorly for bursa. 



The lower extremity, large, expanded, and quadrilateral, 

 presents : 



Carpal articular surface, smooth, concave, triangular depres- 

 sion divided by an antero-posterior ridge into an outer facet for 

 scaphoid bone and inner for semi-lunar; 



