140 



OSTEOLOGY. 



Fig. 93. Plan of the Development of the Radius. 

 By 3 Centres. 



Appears at 



V/A Shaft aba 



from one another by an elevated ridge. The most anterior one gives passage to 

 the tendon of the Extensor ossis metacarpi pollicis, the posterior one to the tendon 

 of the Extensor primi internodii pollicis. The posterior surface is convex, affords 

 attachment to the posterior ligament of the wrist, and is marked by three grooves. 

 The most external is broad, but shallow, and subdivided into two by a slightly 

 elevated ridge. The external groove transmits the tendon of the Extensor carpi 

 radialis longior, the inner one the tendon of the Extensor carpi radialis brevior, 

 Near the centre of the bone is a deep, but narrow, groove, directed obliquely from 

 above downwards and outwards; it transmits the tendon of the Extensor secundi 

 internodii pollicis. Internally is a broad groove, for the passage of the tendons of 

 the Extensor communis digitorum, and Extensor indicis ; the tendon of the Extensor 

 minimi digiti passing through the groove at its point of articulation with the ulna. 

 Structure. Similar to that of the other long bones. 



Development (fig. 98). By three centres: one for the shaft, and one for each 



extremity. That for the shaft makes 

 its appearance near the centre of the 

 bone, soon after the development of 

 the humerus commences. At birth, 

 the shaft is ossified ; but the ends of 

 the bone are cartilaginous. About the 

 end of the second year, ossification 

 commences in the lower epiphysis; 

 and about the fifth year, in the upper 

 one. At the age of puberty, the up- 

 per epiphysis becomes joined to the 

 shaft; the lower epiphysis becoming 

 united about the twentieth year. 



Articulations. With four bones; the 

 humerus, ulna, scaphoid, and semi- 

 lunar. 



Attachment of Muscles. To the tu- 

 berosity, the Biceps ; to the oblique 

 ridge, the Supinator brevis, Flexor 

 digitorum sublimis, and Flexor longus 

 pollicis ; to the shaft its anterior sur- 

 face, the Flexor longus pollicis and 

 Pronator quadratus ; its posterior sur- 

 face, the Extensor ossis metacarpi 

 pollicis, and Extensor primi internodii 

 pollicis; its outer surface, the Pro- 

 nator radii teres; and to the styloid 

 process, the Supinator longus. 



THE HAND. 



The Hand is subdivided into three segments, the Carpus or wrist, the Meta- 

 carpus or palm, and the Phalanges or fingers. 



CARPUS. 



The bones of the Carpus, eight in number, are arranged in -two rows. Those 

 of the upper row, enumerated from the radial to the ulnar side, are the scaphoid, 

 semilunar, cuneiform, and pisiform ; those of the lower row, enumerated in the 

 same order, are the trapezium, trapezoid, magnum, and unciform. 



COMMON CHARACTERS OF THE CARPAL BONES. 



Each bone (excepting the pisiform) presents six surfaces. Of these, the ante- 

 rior or palmar, and the posterior or dorsal, are rough, for ligamentous attachment, 





Afjpeart at Z"*- y'\ 



V TTnitrt with Sliaft a,l.< 



