THE ANTERIOR LIMB 267 



5. Muscles arising from the distal end of the humerus and the 

 radius and ulna and inserted on the hand (extensors and flexors 

 of the hand and of the individual digits). The long insertion 

 tendons pass through perforations of the dorsal carpal and 

 transverse (ventral) carpal ligaments (Fig. 103). 



A. Extensor group. The muscles have a general area of 

 origin from the lateral epicondyle of the humerus and the antero- 

 dorsal or anterolateral surface of the radius and ulna. Insertion 

 dorsal. 



(a) The extensor carpi radialis longus. Origin: Lateral epi- 

 condyle. Insertion: Base of the second metacarpal. 



(b) The extensor carpi radialis brevis. Origin: Lateral epi- 

 condyle. Insertion: Base of the third metacarpal. The 

 muscle is partly fused with the foregoing one, and the 

 tendons are closely associated on the wrist. 



(c) The abductor pollicis. Origin: Anterolateral surface of 

 the radius and ulna. Insertion: Base of the first meta- 

 carpal. The muscle is partly concealed by (e). Its tendon 

 forms a conspicuous cross with those of (a) and (b). 



(d) The extensor pollicis et indicis. Origin: Anterolateral 

 surface of the radius and ulna. Insertion: Ungual phalanx 

 of the pollex and the head of the second metacarpal. Its 

 tendon is the first of five in the centre of the carpus. 



(e) The extensor digitorum communis. Origin: Lateral epi- 

 condyle and proximal end of the ulna. Insertion: By four 

 tendons on all phalanges of the four lateral digits. 



(/) The extensor digiti quarti proprius. Origin: Lateral epi- 

 condyle. Insertion: Ungual phalanx of the fourth digit. 



(g) The extensor digiti quinti proprius. Origin: Lateral epi- 

 condyle and lateral surface of the ulna. Insertion: Head 

 of the fifth metacarpal and base of the first phalanx of this 

 digit. 



{h) The extensor carpi ulnaris. Origin: Lateral epicondyle 

 and proximal portion of the lateral surface of the ulna. 

 Insertion: Base of the fifth metacarpal. 



B. Flexor group. The muscles have a general area of origin 

 from the medial epicondyle of the humerus and the posteroventral 



