io8 THE SUPERIOR EXTREMITY 



Brachialis Anticus). The brachialis arises from the entire 

 width of the anterior aspect of the distal half of the body of 

 the humerus, from the medial intermuscular septum, and from 

 a small part of the lateral intermuscular septum proximal to 

 the brachio-radialis. The origin from the bone is prolonged 

 proximally in two slips which partially embrace the insertion 

 of the deltoid. The fibres converge to be inserted into the 

 base of the coronoid process of the ulna by a short, thick 

 tendon. The muscle lies partly under cover of the biceps 

 brachii, but projects beyond it on each side. It is over- 

 lapped on its medial side by the pronator teres, and on the 

 lateral side by the brachio-radialis and extensor carpi radialis 

 longus. Its deep surface is closely connected to the anterior 

 part of the capsule of the elbow-joint. Its chief nerve of 

 supply, from the musculo-cutaneous^ has already been secured, 

 but it receives also one or two small twigs from the radial 

 (musculo-sptrat) nerve which are given off under cover of the 

 brachio-radialis. It is a flexor of the elbow-joint. 



Dissection.- Separate the brachio-radialis from the brachialis 

 muscle, and dissect out the radial nerve, with the anterior 

 terminal branch of the profunda brachii artery, which lie deeply 

 in the interval between the muscles. There also, in a well- 

 injected subject, the anastomosis between the profunda brachii 

 artery and the radial recurrent artery may be made out ; and 

 the twigs which are given by the radial nerve to the brachialis, 

 the brachio-radialis, and the extensor carpi radialis longus, should 

 be looked for. 



Fossa Cubitalis. The cubital fossa is the hollow in 

 front of the elbow. It is triangular in outline and it 

 corresponds generally with the popliteal fossa at the back 

 of the knee. 



It possesses a roof or superficial boundary ; a floor or 

 deep boundary ; medial and lateral boundaries ; a base and 

 an apex. 



The roof is formed by the deep fascia in which lies 

 the thickened band called the lacertus fibrosus. It is 

 pierced by a communication from the deep veins of the 

 forearm to the median cubital vein. It is covered by the 

 skin and superficial fascia, and upon it, in the superficial 

 fascia, lie a portion of the cephalic vein, a portion of the 

 basilic vein, the median cubital vein, the volar branch of 

 the medial cutaneous nerve of the forearm, and the lateral 

 cutaneous nerve of the forearm. 



