MUSCLES OF THE THORACIC LIMB 
The brachialis is very little curved. 
373 
Its tendon of insertion passes over the 
medial ligament of the elbow and under the ulnar tendon of the biceps and ends 
just proximal to the latter. 
that of the brachialis. 
The tensor fasciz antibrachii is thin and narrow. 
lateral surface of the latissimus dorsi, and ends on the 
olecranon and the fascia of the forearm. 
The triceps has an additional deep head (Caput 
accessorium), which arises just below the head of the 
humerus. The medial head is very long; it arises from 
a mark on the proximal fourth of the medial surface of 
the humerus, just behind the insertion of the teres major 
and latissimus dorsi. A bursa lies on the olecranon in 
front of the common tendon of insertion. 
The brachioradialis is a long, narrow, delicate mus- 
ele, situated superficially on the dorsal surface of the 
forearm. It arises with the extensor carpi on the crest 
above the lateral epicondyle of the humerus, and is in- 
serted into the distal part of the medial border of the 
radius. It is often much reduced, and is sometimes ab- 
sent. It rotates the forearm and paw outward. 
The extensor carpi radialis arises on the lateral con- 
dyloid crest and divides into two parts. The larger lat- 
eral part, the extensor carpi radialis brevis, ends on the 
proximal end of the third metacarpal bone. The medial 
and more superficial part, the extensor carpi radialis 
longus, ends on the second metacarpal bone. (A ten- 
don to the fourth metacarpal may occur.) 
The extensor carpi obliquus or abductor pollicis 
longus arises from the lateral border and dorsal surface 
of the ulna, the interosseous ligament, and the proximal 
part of the lateral border of the radius. It is inserted 
into the first metacarpal bone by a tendon which con- 
tains a small sesamoid bone. It abducts the first digit. 
There are three (or four) extensors of the digits. 
1. The common digital extensor (MM. extensor digi- 
talis communis) arises on the lateral epicondyle of the 
humerus and the lateral ligament of the elbow joint. 
It has four bellies, each of which has a tendon of inser- 
tion. These end on the third phalanges of the second, 
third, fourth, and fifth digits. 
2. The extensor of the first and second digits (M. 
extensor pollicis longus et extensor indicis proprius) is 
small, and is covered by the common and lateral ex- 
tensors. It arises on the proximal half of the ulna. Its 
tendon descends with that of the common extensor and 
divides into two branches. The delicate medial branch 
ends on the first digit, while the larger lateral one ends 
with the tendon of the common extensor for the second 
digit. 
The tendon of the biceps forms a partial sheath for 
It arises on the tendon and 
Fic. 323.—Musctes oF ANTIBRA- 
CHIUM AND Mants or Doe; 
Laterat View. 
a, Triceps brachii; 6, brachi- 
alis: c, extensor carpi radialis; d, 
common digital extensor; d’, d”, 
d’”’, d’””", tendons of preceding; e, 
lateral digital extensor; e’, f, ten- 
dons of preceding; g, ulnaris 
lateralis; h, ulnar head, h’, hu- 
meral head of flexor carpi ulnaris; 
t, extensor carpi obliquus (s. ab- 
ductor pollicis longus); 4&, inter- 
ossei; I, branches from preceding 
to extensor tendons; /, olecranon; 
2, radius; 3, lateral epicondyle of 
humerus. (After Ellenberger, in 
Leisering’s Atlas.) 
3. The lateral digital extensor (M. extensor digitalis lateralis) consists of two 
muscles which are not rarely fused. They arise on the lateral epicondyle of the 
humerus and the lateral ligament of the elbow joint. The larger superficial muscle 
is the extensor of the third and fourth digits (M. extensor digiti tertii et quarti); 
