MUSCLES OF THE FORE ARM. 427 



4. The Extensor Carpi Ulnans, 



Is superficial, and placed principally parallel with the ulna. 

 It arises, tendinous, from the external condyle, fleshy from the 

 inter-muscular ligament, and inside of the fascia. Crossing 

 very obliquely the upper part of the radius and the ulna, it also 

 arises fleshy from the back part of the latter bone. Its fibres 

 terminate obliquely in a tendon which goes through the groove 

 of the ulna, and is there furnished with a bursa. 



It is inserted, by its tendon, into the ulnar side of the base of 

 the metacarpal bone of the little finger. 



It extends the hand.* 



5. The Extensor Digitorum Communis, 



Is superficial, being placed between the extensor ulnaris and 

 the extensor radialis brevior. It arises, tendinous, from the ex- 

 ternal condyle, and fleshy from the inter-muscular ligament of 

 the contiguous muscles. As it approaches the wrist it sends off 

 four tendons, which pass together through a common groove on 

 the back of the radius. On the back of the hand these tendons 

 diverge, and near the roots of the fingers send cross slips to 

 each other. 



Each tendon goes to its respective finger, and covers the 

 whole posterior part of it, being spread out into a membrane 

 which adheres to the phalanges from the root of the first to the 

 root of the last. The precise mode of the insertion of these 

 tendons is as follows : on the back of the first phalanx, the la- 

 teral margins of these tendons are joined by the tendons of the 

 lumbricales and interossei; and the tendinous membrane, thus 

 formed, simply adheres by condensed cellular membrane to the 

 whole back of the first phalanx ; the middle part of this tendon 

 then passes on to be inserted near the articular margin of the 

 base of the second phalanx; and the two lateral parts of the 

 tendinous membrane, after keeping separate for some distance, 



* Varieties. Sometimes its tendon is joined, by a small fasciculus, to the ex- 

 tensor tendon of the little finger. 



