184 



Muscles of tlie Upper Extremity. 



M. extensor digitorum communis (see 

 Fig. 240, 243); it arises from the exter- 

 nal condyle of the humerus and the Fascia 

 antibracJiiij being inserted by four tendons 

 at the dorsum of the first phalanges into 

 the aponeurosis of the second to the fifth 

 fingers. The aponeurosis divides into three 

 slips, of which the middle is inserted into 

 the II. phalanx, the two lateral into the 

 lateral borders of the III. phalanx. 



M. extensor digiti minimi (Fig. 240, 243) 

 has the same origin as the preceding muscle; 

 the tendon of insertion is united with the 

 fourth tendon of the Extensor communis. 



M. extensor carpi ulnaris s. ulnaris exter- 

 nus (Fig. 240) arises from the external 

 condyle of the humerus and the Fascia 

 antibrachii, and is inserted into the base of 

 the metacarpal bone of the little finger. 

 (Extensor and abductor of the hand.) 



M. extensor ossis metacarpi pollicis s. 

 abductor pollicis longus arises from the middle 

 portion of the posterior surface of the ulna, 

 the outer surface of the interosseous liga- 

 ment and the radius ; it is inserted into 

 the base of the metacarpal bone of the 

 thumb. 



M. extensor primi internodii pollicis s. 

 extensor pollicis Ircvis has the same origin 

 as the preceding, and is inserted into the 

 dorsal aponeurosis of the first phalanx of 

 the thumb (Fig. 243). 



M. extensor secundi internodii ^o///c/s s. 

 extensor pollicis longus arises from the crest 

 of the ulna and the interosseous membrane, 

 and is inserted into the dorsal aponeurosis 

 of the second phalanx of the thumb (Fig.243). 



M. extensor indicts s. indicator arises from 

 the crest and outer surface of the ulna ; 

 it unites with the tendon of the index 

 244. The Muscles at finger of the M. extensor digitorum communis 



the Outer Side of (Fig. 243). 

 the Forearm. 



