Limbs : Upper Limb 



like a thick disc, with a concave articular surface above for the capitulum of the 

 humerus, and a peripheral articular surface for the lesser sigmoid cavity of the ulna 

 and the orbicular ligament which surrounds it and holds it in this cavity. The head 

 is connected by the narrow neck with the shaft, and this bears, just below the neck and 

 on the inner side, the tubercle for the insertion of the Biceps : here the shaft is some- 

 what cylindrical, giving insertion ex- 

 ternally, in front, and behind to Supi- 

 nator brevis, and this area is limited in 

 front and behind by anterior and pos- 

 terior oblique lines : Flexor sublimis 

 arises from the anterior line. On the 

 outer and back surface, where these 

 lines approach each other, and about 

 half-way down, is a rough Pronator 

 teres impression. Below the oblique 

 line the shaft has a hollowed anterior 

 surface for origin of Flexor longus 

 polh'cis, bounded internally by the inte- 

 rosseous border, externally by the outer 

 border continuous with the anterior 

 oblique line, and below by a pronator 

 ridge and a quadrate surface, comparable 

 with that on the ulna, for Pronator 

 quadratus. The posterior surface is 

 rounded from side to side, and shows 

 markings for Extensor ossis metacarpi 

 pollicis and Ext. brevis pollicis near 

 the interosseous border. Lower down 

 this posterior surface widens into the 

 lower end, and here presents grooves for 

 tendons. The lower end is enlarged by 

 the addition of a mass on its outer side, 

 which projects down in the styloid pro- 

 cess, for the external lateral ligament. 

 As a result the lower end has an outer 

 surface on the styloid process for thumb 

 extensor tendons, a postero-external 

 behind it, carrying the radial extensor 

 tendons, a posterior internal to this, 

 marked by an oblique groove for Ext. 

 longus pollicis, and a broad and shallow 

 one for the common and index exten- 

 sors ; an internal, carrying a concave 



sigmoid cavity (which plays round the head of the ulna) on its lower part and a non- 

 articular triangular area above this, where some fibres of Pronator quadratus are 

 inserted : also an anterior rough for ligamentous attachments, and an inferior, which 

 articulates with the carpus. The articular surface on the inner side is not continuous 

 with that below, being separated from it in the recent state by the attachment of the 

 base of the triangular nbro-cartilage to the intervening border. 



The radius is held to the ulna by certain bands of connection, which, while keeping 



FIG. 71. Right radius. S.B. insertion of Supina- 

 tor brevis ; E.M., E.B.P. origins of Extensor 

 ossis and brevis pollicis ; P.Q. Pronator quadra- 

 tus insertion. To tell right from left, hold the 

 bone with the head up, the tubercle internally, 

 and the concave aspect of the lower third 

 forward. 



