MUSCULAR SYSTEM. 137 



cartilaginous eminence in the middle of that groove. At tliis 

 part the tendon pierces the capsular ligament of the shoulder 

 joint, from the internal cavity of which it is separated only by a 

 reflection of synovial membrane. The anterior surface of the 

 tendon exhibits a few pale fleshy fibres running upon it. The 

 fleshy belly of the muscle is invested by an aponeurotic sheath, 

 and appears as if it were made up of several very small cylindrical 

 muscles, similarly invested, and afterwards joined together into 

 one body. Its inferior attachments are wholly tendinous in one 

 place, aponeurotic in another. 



Action. — To bend the arm, by carrying it forwards and upwards. 



HUMERALis EXTERNus. — ( Humero-radialis obliquus.) 



Situation. — Deep-seated upon the infero-external side of the 

 shoulder. 



Form. — Oblong ; twisted. 



Attachment. — Superiorly, to the entire postero-external parts 

 of the neck and body of the humerus : inferiorly, to the supero- 

 anterior part of the body of the radius, immediately below the 

 attachment of the flexor brachii. 



Relations. — Externally, with the middle head of the triceps; 

 internally and posteriorly, with the humerus ; anteriorly, with the 

 flexor brachii. 



Direction. — Curvilinear and oblique. 



Structure. — Fleshy ; excepting a single tendinous intersection 

 through its inferior part, which proceeds to its termination. 



Action. — To assist in the flexion of the arm. 



5 —POSTERIOR HUMERAL REGION, 



Comprehends a mass of muscle, at the back of the humerus, 

 of considerable bulk, and partially divisible into three portions ; 

 on which accounts, and from its having different attachments, it 

 is found most convenient, and indeed is most usual, to consider the 

 muscle (which altogether has the name of Triceps Extensor 

 Brachii) under three distinct heads or divisions. These heads 

 are distinguished by epithets correspondent to their magnitude 

 and importance. 



TRICEPS EXTENSOR BRACHII. 

 Having three divisions or heads: the first is the 



CA PUT INI AG N u M.~- Scapulo-okcranius. 



Situation. — Infero-posterior part of the shoulder : occupying 

 the angular interspace between the scapula and humerus. 

 For/n. — Broad ; thick ; triangular ; flattened. 



T 



