ANTERIOR BRACHIAL REGION. 



231 



scapula. The three heads unite to form a broad muscle, which is inserted 

 by an aponeurotic tendon into the olecranon process of the ulna ; a small 

 bursa is situated between its tendon and the upper part of the olecranon. 



The scapular head of the triceps passes between the teres minor and 

 major, and divides the triangular space between those two muscles into 

 two smaller spaces, one of which is triangular, the other quadrangular. 

 The triangular space is bounded by the teres minor, teres major, and 

 scapular head of the triceps ; it gives passage to the dorsalis scapulae ar- 

 tery and veins. The quadrangular space is bounded on three sides by 

 the three preceding muscles, and on the fourth by the humerus. Through 

 this space pass the posterior circumflex artery and veins, and circumflex 

 nerve. 



A few of the deep fibres of the triceps, attached above to the humerus 

 and below to the capsule of the elbow joint, have been named sub-anco- 

 neus ; they are analogous to the sub-crureus. 



Relations. By its posterior surface with the deep and superficial fascia 

 and integument. By its anterior surface with the superior profunda artery, 

 musculo-spiral nerve, humerus, intermuscular aponeuroses which separate 

 it from the brachialis anticus, and with the elbow joint. The scapular 

 head is in relation posteriorly with the deltoid and teres minor ; anteriorly 

 with the subscapularis, teres major, and latissimus dorsi; and externally 

 with the posterior circumflex vessels and nerve. 



Actions. The triceps is an extensor of the fore- Fi s- 122 -* 



arm. 



Anterior Brachial Region. 



Superficial Layer. 

 Pronator radii teres, 

 Flexor carpi radialis, 

 Palmaris longus, 

 Flexor sublimis digitorum, 

 Flexor carpi ulnaris. 



Dissection. These muscles are brought into view 

 by making an incision through the integument along 

 the middle line of the fore-arm, crossing each extre- 

 mity by a transverse incision, and turning aside the 

 flaps. The superficial and deep fascia are then to be 

 removed. 



The PRONATOR RADII TERES arises by two heads ; 

 one from the inner condyle of the humerus, fascia of 

 the fore-arm, and intermuscular aponeurosis ; the 

 other from the coronoid process of the ulna ; the me- 

 dian nerve passing between them. Its tendon is flat 

 and inserted into the middle third of the oblique ridge 

 of the radius. The two heads of this muscle are best 

 examined by cutting through that which arises from 

 the inner condyle, and turning it aside. The second 

 head will then be seen with the median nerve lying 

 across it. 



Superficial layer of the muscles of the fore-arm. 1. The lower part of the biceps, 



ts tendon. 2. A part of the brachialis arnica's, seen beneath the biceps. 3. A par, 



f the triceps 4. The pronator radii teres. 5. The flexor carpi radial. 6 The pal 



