176 THE MUSCLES. 



(//'), which divides immediately into three or four (Fig. 84, b). 

 These pass through the groove on the uhiar side of the dorsal 

 surface of the radius and diverge to the digits lying beneath 

 the extensor communis tendon. 



Inscrlion (Fig. 84, b). — The three tendons on the ulnar 

 side join the ulnar sides of the tendons of the extensor com- 

 munis (a) at their insertions. The radial of the four tendons 

 (not always present) joins the tendon of the extensor indicis (c) 

 and may also give a branch to the radial side of the base of the 

 first phalanx of the third digit. 



Relations. — Outer surface with the integument. Radial 

 border with the extensor communis digitorum (;;/) ; ulnar border 

 with the extensor carpi ulnaris {i)). Inner surface with the 

 supinator (Fig. 85, b) and the extensor brevis pollicis (Fig. 

 85, a); distad with the extensor indicis (Fig. 85, c). 



Action. — Extensor of the four ulnar digits. 



M. extensor carpi ulnaris (Fig. 75, o). 



Origin. — (i) By a short, broad tendon from the distal por- 

 tion of the lateral epicondyle of the humerus (Fig. ^1,0) distad 

 of the origin of the extensor lateralis, and (2) by a smaller 

 tendon from the ulna at the dorsal tip of the semilunar notch 

 (Fig. 86, e). 



The muscle passes along the ulnar side of the forearm 

 dorsad of the extensor digitorum lateralis (//). It ends near 

 the junction of the middle and distal thirds of the forearm in a 

 large, flat tendon {0') which is closely adherent to the ligaments 

 of the wrist and which passes over the distal end of the ulna to 

 its 



Liscrtion into the tubercle on the ulnar side of the base of 

 the fifth metacarpal (Fig. 84, g). 



Relations. — Outer surface with the integument. Radial 

 (or ventral) border with the extensor digitorum lateralis (Fig. 

 75, ;/) ; ulnar (or dorsal) border with the flexor profundus digi- 

 torum {(]). Inner surface with the radius, the extensor indicis 

 Fig. 85, c), and the extensor pollicis brevis (Fig. 85, a). 



Actio7i. — Indicated by its name. 



M. extensor indicis (proprius) (Fig. 85, c; Fig. 75,/) (in- 

 cludes extensor pollicis longus also). 



