176 THE MUSCLES. 
(z'), which divides immediately into three or four (Fig. 84, 4). 
These pass through the groove on the ulnar side of the dorsal 
surface of the radius and diverge to the digits lying beneath 
the extensor communis tendon. 
Insertion (Fig. 84, 6).—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 (0). Inner surface with the 
supinator (Fig. 85, 4) and the extensor brevis pollicis (Fig. 
85, @); distad with the extensor indicis (Fig. 85, ¢). 
Action.—Extensor of the four ulnar digits. 
M. extensor carpi ulnaris (Fig. 75, 0). 
Origin.—(1) By a short, broad tendon from the distal por- 
tion of the lateral epicondyle of the humerus (Fig. 81, ¢) 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 (z). 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 
Insertion 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, 2); ulnar (or dorsal) border with the flexor profundus digi- 
torum (g). Inner surface with the radius, the extensor indicis 
Fig. 85, c), and the extensor pollicis brevis (Fig. 85, a). 
Action.—Indicated by its name. 
M. extensor indicis (proprius) (Fig. 85, c; Fig. 75, p) (in- 
cludes extensor pollicis longus also). 
