FOREARM AND HAND 135 



M. Extensor Digitorum Communis. The extensor digi- 

 torum communis takes origin by the common tendon 

 from the lateral epicondyle of the humerus. The deep 

 fascia and the intermuscular septa in relation to it also 

 contribute fibres. Its fleshy belly, in the lower part of the 

 forearm, sends out four tendons, which pass under cover of 

 the dorsal carpal ligament. On the dorsum of the hand 

 they diverge and proceed onwards to the four fingers. Their 

 arrangement and attachments on the dorsum of the hand and 

 fingers will be afterwards considered (p. "145). This muscle is 

 supplied by the dorsal interosseous nerve. 



M. Extensor Digit! Quinti Proprius (O.T. Extensor 

 Minimi Digiti). The extensor digiti quinti proprius is a 

 slender fleshy belly which at first sight appears to be a part of 

 the preceding muscle, but its tendon passes through a special 

 compartment in the dorsal carpal ligament. It arises in 

 common with the extensor digitorum communis, and is 

 supplied by the dorsal interosseous nerve. 



M. Extensor Carpi Ulnaris. The extensor carpi ulnaris 

 arises, by means of the common extensor tendon, from 

 the lateral epicondyle of the humerus, from the fascia 

 of the forearm, and from the intermuscular septum between 

 it and the extensor digiti quinti proprius. In the middle 

 third of the forearm it receives some fibres from the strong 

 fascial layer which binds it to the dorsal border of the 

 ulna. The tendon does not become free from the fleshy 

 fibres until it approaches close to the wrist. It occupies 

 the groove on the dorsal aspect of the distal end of the 

 ulna, between the head and styloid process, and passing 

 under cover of the dorsal carpal ligament is inserted into the 

 tubercle on the base of the metacarpal bone of the little 

 finger. This muscle is supplied by the dorsal interosseous 

 nerve. 



M. Anconseus (Anconeus). The anconaeus is a short 

 triangular muscle placed on the dorsal aspect of the elbow-joint. 

 It presents a narrow origin from the posterior aspect of the 

 lateral epicondyle of the humerus. From this its fibres 

 spread the upper fibres passing transversely medially, 

 whilst the others proceed medially and distally with an 

 increasing degree of obliquity towards its distal end. It is 

 inserted into the lateral surface of the olecranon, and into 

 the proximal third of the dorsal surface of the body of the ulna. 



