4o6 A MANUAL OF ANATOMY 



and outwards. The interval between it and the upper border of 

 the interosseous membrane gives passage to the posterior inter- 

 osseous vessels. 



Movements. — The movements allowed are pronation and supination, the 



latter being the stronger. In pronation the lower part of the radius, carrying 

 with it the hand, crosses over the lower part of the ulna so as to lie on its inner 

 side, the dorsum of the hand being directed upwards. In supination the 

 radius and hand retrace their steps, so that the lower part of the radius lies 

 on the outer side of the ulna, the palm of the hand being directed upwards. 

 At the superior radio-ulnar joint the head of the radius rotates upon the capi- 

 tellum of the humerus within the orbicular ligament, and comes into closest 

 relation with the capitellum in semiflexion of the elbow-joint and semi- 

 pronation of the forearm. At the inferior radio-ulnar joint the radius, 

 carrying with it the triangular fibro-cartilage, rotates upon the head of the 

 ulna, the movement being one of limited circumduction around an axis passing 

 from the centre of the head of the radius to the styloid process of the ulna. 

 There is also a limited amount of circumduction on the part of the ulna, the 

 lower end of that bone moving outwards and backwards in pronation, and 

 inwards and forwards in supination. 



Muscles concerned in the Movements — (i ) Pronation. — The principal pronator 

 muscles are the pronator radii teres and pronator quadratus. (2) Supination. 

 — The principal supinator muscles are the biceps and supinator radii brevis. 

 The brachio-radialis is also a feeble supinator, but it only acts as such to 

 the extent of semisupination. The biceps is enabled to act as a supinator in 

 virtue of its insertion into the back part of the bicipital tuberosity of the radius. 



THE ARTICULATIONS OF THE HAND. 



Carpal Joints. — The carpal joints are divided into those of the 

 first row, those of the second row, and the transverse carpal 

 joint. 



Joints of the First Row. — ^These belong to the class diarthrosis,, 

 and to the subdivision arthrodia. The bones of the first row, with! 

 the exception of the pisiform, are united by two dorsal, two palma^ 

 and two interosseous ligaments. The dorsal and palmar ligament 

 extend transversely from the front and back of the semilunar to th^ 

 corresponding surfaces of the scaphoid and cuneiform. The twc 

 interosseous ligaments are placed one on either side of the semilunar 

 and they connect it with the scaphoid and cuneiform. They an 

 situated high up on the lateral surfaces of the bones, and thei 

 upper surfaces form part of the lower wall of the radio-carpal joint 



The synovial membrane is continuous with that of the transversi. 

 carpal joint. 



Pisiform Joint. — The pisiform bone is united to the front of th 

 cuneiform by a capsular ligament, which surrounds the joint and i 

 attached to the bones at the circumference of their opposed articula 

 surfaces. Superiorly the capsule is connected with the tendon C' 

 insertion of the flexor carpi ulnaris, and interiorly with two prolongs 

 tions of that tendon, called the pisi-uncinate and pisi-metacarfx 

 ligaments. The former is attached to the hook of the unciform bon^ 

 and the latter to the base of the fifth metacarpal. These ligamen 



