214 



OSTEOLOGY. 



OLECRANON 



SUBCUTANEOUS 



SURFACE 



-HEAD 



NECK 



TUBEROSITY 



INTEROSSEOUS 



CREST 



POSTERIOR 

 OBLIQUE LINE 



forms an epiphysis which unites with the body about sixteen. In this connexion Fawcet 

 (Proc. Anat. Soc. Great Britain and Ireland, 1904, p. xxvii) has described the occurrenc 



of two ossific centres in th 

 olecranon. One, the mor 

 volar, the "beak centre," enter 

 into the formation of th 

 proximal end of the artici 

 lar surface of the semiluna 

 notch, the other centre, nc 

 in any way forming it. j 

 scale-like centre appears in th 

 cartilage of the head abou 

 the sixth year, from which th 

 distal surface of that part c 

 the bone is developed, and b 

 the extension of which th 

 styloid process is also ossified 

 this epiphysis does not unit 

 with the shaft till the twer 

 tieth or twenty -third yeai 

 Independent centres for th 

 styloid process and for th 

 extreme edge of the olecrano: 

 have also been described. Th 

 student may here be warnei 

 that the epiphysial line b< 

 tween the shaft and proxima 

 or olecranon epiphysis doe 

 not correspond to the cor 

 stricted part of the semiluna 

 notch, but lies considerabl; 

 proximal to it. 



The Radius. 



The radius, or latera 

 bone of the forearm, ii 

 shorter than the ulna, witl 

 which it is united on thi 

 medial side. Proximally i 

 articulates with the hum 

 erus, and distally it supports 

 the carpus. It consists o: 

 a head, a neck, a tufoerosity 

 a body, and an expandec 

 distal extremity. The bod} 

 is narrow proximally, but in 

 creases in all its diameter; 

 distally. 



Proximal Extremity 

 The capitulum (head) i 

 disc-shaped and provide* 

 with a shallow concave sur 

 face (fovea capituli radii 

 proximally for articulatioi 

 with the capitulum of th: 

 humerus. The circumfei; 

 ence of the head (circum 

 ferentiaarticularis) issmoot"- 

 and is embraced by the annular ligament. On the medial side it is usually muc'i 

 broader, and displays an articular surface, Diane in the proximo-distal direction 



HEAD 

 STYLOID PROCESS 



Ext. poll, 

 long. 



Ext. poll, brevis 



Ext. carpi rad. 

 longus 



Ext. carpi rad. 

 brevis 



STYLOID PROCESS 



GROOVE FOR EXT. Ext. dig. commun. 

 CARPI ULNARIS and ext. indicis proprius 



FIG. 206. THE RIGHT RADIUS AND ULNA SEEN FROM THE DORSAL 

 ASPECT 



