38 HANDBOOK OF ANATOMY 



4. Extens<jr communis digi-^j 



torum Vin the fourth groove. 



Extensor indicis 



5. Extensor minimi digiti in the groove between the ulna and 



radius. 



6. Extensor carpi ulnaris in the groove of the ulna. 



Digital Sheaths, strong fibrous sheaths which hold down the 

 flexor tendon of the fingers. They are attached along the edges 

 of the palmar surfaces of the phalanges and interphalangeal 

 joints, and continuous with the palmar fascia. 



The Axilla is the hollow space in the armpit through which 

 the axillary vessels and the cords of the brachial plexus pass to 

 reach the arm. It is cone-shaped, with the apex upwards. 



The apex is bounded by the superior border of the scapula, 

 the first rib, and the clavicle, and is covered in by the costo- 

 coracoid membrane. 



The floor is formed of the deep fascia. 



The posterior wall is formed by subscapularis, teres minor, 

 teres major, and latissimus dorsi, the lower free edge of which 

 is called the posterior fold. 



The anterior wall is formed by pectoralis major, the lower free 

 edge of which is called the anterior fold. 



The inner wall is formed by the upper digitations of the 

 serratus magnus. The outer wall is formed by the long head of 

 triceps and the humerus. 



The contents are the axillary vessels, the cords of the brachial 

 plexus with their branches, some lymphatic glands and fat. 



The Antecubital Fossa is the triangular space in front of the 

 elbow-joint, covered in by deep fascia and the bicipital fascia. 

 Its boundaries are, above, a line drawn between the condyles of 

 the humerus, on the inner side pronator radii teres, and on the 

 outer side brachio-radialis. 



In the fossa the brachial artery breaks up into its branches. 



