FOREARM AND HAND 133 



Superficial Muscles. The muscles in this region consist 

 of a superficial and a deep group. The superficial muscles, 

 as we proceed from the lateral to the medial border of the 

 forearm, are: (i) the brachio-radialis ; (2) the extensor 

 carpi radialis longus ; (3) the extensor carpi radialis brevis; 

 (4) the extensor digitorum communis ; (5) the extensor digiti 

 quinti proprius; (6) the extensor carpi ulnaris; and (7) the 

 anconaeus. This group therefore comprises one flexor of 

 the elbow, three extensors of the wrist, two extensors of the 

 fingers, and a feeble extensor of the forearm at the elbow- 

 joint, viz. the anconaeus. In the lower part of the forearm 

 the extensor digitorum communis is separated from the 

 extensor carpi radialis brevis by a narrow interval, and in 

 this appear two muscles belonging to the deep group. These 

 turn round the lateral margin of the forearm, upon the surface 

 of the radial extensors of the wrist, and end in tendons which 

 go to the thumb. The proximal muscle is the abductor pollicis 

 longus, and the distal muscle the extensor pollicis brevis. 

 They are placed in close contact, and so intimately are their 

 tendons connected that in many cases they appear at first 

 sight to be blended together by their margins. 



Four of the superficial muscles arise by a common origin 

 from the anterior part of the lateral epicondyle of the humerus, 

 and at the same time derive fibres from the investing fascia 

 and the septa it sends in between them. These are the 

 extensor carpi radialis brevis, the extensor digitorum com- 

 munis, the extensor digiti quinti proprius, and the extensor 

 carpi ulnaris. The superficial muscles should be cleaned, 

 and isolated as far as possible from each other. 



M. Brachio-radialis (O.T. Supinator Longus). This muscle 

 lies more on the volar than on the dorsal surface of the forearm. 

 It takes origin in the arm from the proximal two-thirds of the 

 lateral epicondylar ridge of the humerus and from the lateral 

 intermuscular septum. Near the middle of the forearm a 

 flat tendon emerges from its fleshy belly, and this proceeds 

 distally to gain insertion into the lateral aspect of the 

 expanded distal extremity of the radius at the base of 

 the styloid process. The nerve of supply to this muscle 

 comes from the radial nerve (musculo-spirat). 



M. Extensor Carpi Radialis Longus (O.T. Extensor Carpi 

 Radialis Longior). The long radial extensor of the carpus 

 is placed dorsal to the brachio-radialis. It arises, from the 



