DISSECTION OF THE UPPER EXTREMITY 107 



First Compartment. 



Tendons of M. abductor pollicis longus and M. extensor pollicis brevis. 



Vagina tendinum Mm. abductoris longi et extensoris brevis pollicis. 

 Second Compartment. 



Tendons of Mm. extensor carpi radialis longus et brevis. 



Vagina tendinum Mm. extensorum carpi radialium. 

 Third Compartment. 



Tendon of M. extensor pollicis longus. 



Vagina tendinis M. extensoris pollicis longi. 

 Fourth Compartment. 



Tendons of M. extensor digitorum communis and M. extensor indicis 

 proprius. 



Vagina tendinum Mm. extensoris digitorum communis et extensoris 



indicis. 

 Fifth Compartment. 



Tendon of M. extensor digiti quinti proprius. 



Vagina tendinis M. extensoris digiti V. 

 Sixth Compartment. 



Tendon of M. extensor carpi ulnaris. 



Vagina tendinis M. extensoris carpi ulnaris. 



Note the variable extent of the vaginae tendinum into the dorsum 



manus. (Spalteholz, Fig. 369.) 



Tendons of Extensor Muscles of Fingers. (Spalteholz, Fig. 361 ; 

 Poirier et Charpy, t. ii., Figs. 109, no.) 



Note the divergence of the tendons after leaving the osteo- 

 fibrous canals at dorsum of wrist. At level of head of each meta- 

 carpal bone find fibrous expansion going from deep surface of 

 tendon, becoming adherent to capsula articularis, and inserted 

 into base of first phalanx. At this level note union of process of 

 deep palmar fascia with lateral sides of tendon. Note aponeu- 

 rotic expansion at sides of each tendon over first phalanx and 

 find insertions of Mm. interossei and Mm. lumbricales into these. 

 Observe division of tendon (reinforced by " dorsal expansion") 

 into three tongues of fibrous tissue, the middle one becoming 

 directly inserted into base of phalanx II. ; the lateral tongues, 

 stronger, go farther, become united over the second phalanx, 

 and are inserted into the base of phalanx III. (ungual phalanx). 

 Study the aponeurotic bridges (juncturae tendinum) uniting one 

 tendon with its neighbor. Why is the independent movement of 

 the ring-finger backward so limited ? 



In the thumb, the tendons of the two extensors are placed side 

 by side at the level of the metacarpophalangeal joint and receive 

 the same expansions of the palmar fascia and also interosseous 

 muscles (represented here by the M. abductor pollicis brevis and 

 the M. interosseus I.). 



