Muscles of the Arm. 



323 



Radius 



Processus styloideu 

 ulnae 



Proeessiis stvloideus radii 



Ligameiita 

 intercarpea dorsalia 



Os metacarpal e \ 



Mm. interossei _s; 

 dorsales 



Tendines 



111. extensoris 



digitorum -= 



communis 



(cut off) 



Phalanx I ' 



368. Mm. interossei dorsales manus dextrae. 



Mm. interoissei dorsales (see also Figs. 361 and 367), four flat triangular, penniform, 

 small muscles. Position: in the interspaces between the ossa metacarpalia, nearer the back 

 of the hand. Origin: each comes from the neighboring surfaces of the ossa metacarpalia 

 (see also Fig. 151). Insertion: each of the narrow tendons runs dorsalward fi'om the lig. 

 capitulorum transversuin (see Fig. 241) the first and second each on the radial side of the 

 2nd and 3rd finger, the third and fourth each on the ulnar side of the 3rd and 4*'! finger, 

 to the back of the first phalanx and to the triangular expansion of the corresponding tendon 

 of the m. extensor digitorum communis (see also Fig. 361). Action: the first and second draw 

 the 2nd and 3'"d finger radialward, the third and fourth draw the 3rd and 4<'i finger ulnarward ; 

 aU flex the first phalanx and extend the second and third phalanx of the 2nd 4th finger. 

 Innervation: ramus profundus of the ramus volaris manus n. ulnaris. 



Yagina teudinuin mm. abduetoris longi et extensoris brevis polliois, ragiua 

 tcndinum mm. exteiisoriim carpi radialium, Tagina tendinis m. extensoris pollicis 

 longi (communicating constantly witli the preceding), vagina tendinis m. extensoris digit! 

 quiuti and vagina tendinis m. extensoris carpi iiluaris fsee Fig. 369) surround thejj; 

 corresponding tendons at the lig. carpi dursale and for varying distances b^'luw it. 



Vagina tendiuum mm. extensoris digitorum communis et extensoris in^icis 

 (see Kg. 369) forms a sheath for the tendons of these muscles in common as far as the middle 

 of the ossa metacai-paha. 



