66 ANATOMY OF THE WOOD EAT 



connection of the deeper fibers between them. They all 

 arise from the lateral epicondyle of the humerus proximad 

 to the origin of the extensor digiti quinti. The tendons 

 are stouter than in Homodontomys and as usual, all pass in 

 a cluster beneath the transverse ligament. The more 

 lateral head of this muscle develops a single tendon which 

 splits in two, one branch passing to the medial dorsum of 

 digit five and the other to the lateral dorsum of digit three. 

 The head next mediad is the deepest of the three, with 

 shortest belly. From the fibers extend two tendons which 

 pass to the medial dorsum respectively of digits three and 

 four. The most medial head develops a single tendon 

 which extends to the medial dorsum of digit two. Due to 

 the tenuousness of the distal ends of these tendons one 

 can not be positive whether the insertion is upon the first 

 or second phalanx. 



M. extensor metacarpi pollicis (figs. 13, 15, 28) is 

 a bipennated muscle arising deep to the extensor carpi 

 uLnaris. It has origin from the proximal three-fifths of 

 the radial surface of the ulna and half the ulnar surface of 

 the radius. The broad tendon extending from it passes 

 obliquely mediad from beneath the tendons of the ex- 

 tensor digitorum communis, over the tendons of the two 

 extensores carpi radiales, and to its insertion upon the 

 medial base of metacarpus one. 



M. extensor indicis (figs. 15, 28). Origin of this very 

 slender muscle is from the proximal half of the dorso- 

 cranial border of the lateral ridge of the ulna deep to the 

 extensor carpi ulnaris. Its tendon passes over the carpal 

 groove beneath the tendons of the extensor digitorum 

 communis, and splitting in two, the more robust branch 

 passes to the lateral dorsum of digit two, while a broader, 

 though very thin and transparent, extension is inserted 

 upon digit one. 



M. extensor digiti quinti (figs. 13, 15, 28) Hes dorso- 



