The Anterior Limb. 213 



B. Flexor group. The muscles arise in front of the axis of the 

 humerus and are inserted on the radius and ulna in front of the 

 elbow-joint. 



(a) The biceps brachii. Origin: Anterior border of glenoid 

 cavity. Insertion: Ventromedial surface of the ulna and 

 medial surface of the radius. The muscle possesses only one 

 head in the rabbit. 



(b) The brachialis. Origin: Anterior and lateral surfaces of 

 the humerus, divided unequally, into a larger lateral and a 

 smaller medial portion by the insertion tendons of the 

 deltoideus and atbductores rriuscles. Insertion: In common 

 with the biceps. 



6. 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. 75). 



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 

 epicondyle. Insertion: Base of the second metacarpal. 



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

 epicondyle. 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 poUicis. 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 poUicis et indicis. Origin: Anterolateral 

 surface of the radius and ulna. Insertion: Ungual phalanx 

 of the poUex 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 

 epicondyle and proximal end of the ulna. Insertion: By 

 four tendons on all phalanges of the four lateral digits. 



