164 SPECIAL ANATOMY. 



arm, Art. radial., which commences beneath it. Or.: l.Marg. 

 extern, oss. humeri (inferior one-fourth). 2. Lig.intermuscular. 

 and Condyl. extern. Ins. : Basis proc. styloid. Radii. Use : 

 rotates the radius outwards until, at last, it rather flexes the fore- 

 arm. 



Nerves : radialis, inteross. extern. 



309. 10. Extensor carpi radialis longus (s. radialis 



externus longus). 



Pos. : For two-thirds of its length covered above by the last 

 muscle, above and upon the carpus by M. abductor and extensor 

 pollic. long., on its inner edge passes Art. radial. Or. : Angul. 

 externus humeri Lig. intermusculare externum. Ins. : Os 

 Metacarpi II. (Basis, dorsal surface). 



310. 11. Extensor carpi radialis brevis. 



Pos. : beneath the last muscle, covers the outer surface of the 

 Radius; to the inner side of m. extensor digit, commun. Or. : 

 1. Condylus extern, humeri. 2. Fascia cubiti. Ins. : Os me- 

 tacarpi III. (Basis, dorsal surface). Use: to extend, like the 

 former muscle, the hand, and draw it towards the radial side 

 (that is, it abducts it). 



Nerves : (tenth and eleventh) radial, superftc. and profund. 



311. 12. Supinator brevis. 



Pos. : broad, on the superior half of the radius, winding around 

 it, obliquely from above downwards ; beneath ancon&us parvus, 

 extensor digit, commun. and carpi ulnar. Or.: 1. Lig.laterale 

 extern. 2. Mar go extern. Ulnse (below fossa sigmoid.). Ins.: 

 Radius (anterior inner surface one half). Use : rotates the upper 

 half of the radius outwards. 



Nerves: inteross. extern. [This muscle is perforated by a branch of the 

 radio-spiral nerve.] 



c. Muscles upon the dorsal surface, 

 a. Superficial layer. 



312. 13. Extensor digitorum communis. 



Pos. : between m. extens. carpi radial, breve and ulnaris, 

 covers M. supinat. brevis, abduct, long, and brevis, extensor 

 long, pollicis, extens. indicis, the back of the carpus, the meta- 

 carpus, and fingers. Or. : Condyl. extern, humeri. Ins. : Pha- 

 lang. II. and III. of the second to the fifth finger ; four tendons, 

 each of which divides into three portions. The tendon of the 

 second finger is more free than the rest. Use : to extend the 

 second, third, fourth, and fifth fingers. 



Nerves : inteross. extern, and radial, dorsal. 





