MUSCLES OF THE THORACIC LIMBS. 173 
flexor muscles. Distad of the transverse ligament the fascia 
spreads out in the palm of the hand, and becomes united with 
the fibrous pad which is situated here. On the fingers the 
fascia becomes attached to the phalanges, forming tendinous 
sheaths, the so-called vaginal ligaments, for the flexor 
muscles. Near the base and the head of the first phalanx 
strong, narrow, ring-like bands, the annular ligaments (Fig. 
88, 2), are formed in these sheaths; these surround and bind 
down the tendons of the flexor muscles. 
A. MUSCLES ON THE ULNAR AND DORSAL SIDE OF THE 
FOREARM (extensors and supinators) (Fig. 75, p. 158). 
M. brachioradialis or supinator longus (Fig. 75, &; Fig. 
77, n).—This is a ribbon-like muscle lying on the lateral side 
of the brachium and the ventrolateral border of the antibra- 
chium just beneath the superficial fascia. It connects the 
humerus and the radius. 
Origin.—By a thin tendon from about the middle fifth of 
the dorsal border of the humerus, or sometimes proximad of 
the middle. The muscle curves over the outer surface of the 
’ brachialis (Fig. 75, 2), to which it is closely applied, and runs 
along the lateral border of-the antibrachium to its insertion. 
Insertion by a short tendon into the ridge which forms the 
ventral limit of the groove on the outer surface of the styloid 
process of the radius and upon the adjacent ligaments. 
Relations.—Outer surface with the integument, and at the 
proximal end with the caput laterale of the triceps (Fig. 75, /). 
Inner surface with the brachialis (2), the extensor carpi radialis 
longus (/) and brevis, and the extensor communis digitorum (7). 
Action. —Supinator of the hand. 
M. extensor carpi radialis longus (Fig. 75, /; Fig. 77, 
o).—This lies along the radial side of the forearm, and con- 
nects the humerus and the second metacarpal. f 
Origin (Fig. 81, &) from the middle portion of the lateral 
supracondyloid ridge between the origin of the brachialis (7) 
and the anconeus. About the middle of the forearm the 
muscle ends in a slender tendon (Fig. 84, e) which passes 
through the groove on the radial side of the dorsal surface of 
the distal end of the radius. 
