THE UPPER LIMB 329 



On account of the existence of the acromio- clavicular joint, the 

 direction of the glenoid cavity of the scapula remains unaltered 

 during the movements of the bone. 



Chief Muscles concerned in the Movements. — Elevation of Entire 

 Scapula : Cervical part of the trapezius, and the levator anguli 

 scapulae. Depression of Entire Scapula : The lower fibres of the 

 trapezius, which end upon the somewhat triangular tendon, and 

 the pectoraUs minor. Outward or Forward Movement of Entire 

 Scapula : The serratus magnus. Inward or Backward Movement 

 of the Entire Scapula : The middle and lower parts of the trapezius, 

 and the rhomboid muscles. 



Special Movements. — Elevation of Acromion : Cervical pari of the 

 trapezius. Elevation of Superior Angle: Levator anguli scapulae, 

 aided by the rhomboid muscles. 



The inferior angle of the scapula is kept in contact with the dorsal 

 wall of the thorax by the upper horizontal fibres of the latissimus 

 dorsi muscle, which pass over its dorsal aspect. 



The base of the scapula is kept in contact with the dorsal wall of 

 the thorax by the serratus magnus and rhomboid muscles. 



THE ARM. 



Landmarks. — ^The front of the brachial region presents a well- 

 marked elongated prominence, due to the biceps, which reaches 

 from the anterior fold of the axilla to near the elbow. Internal to 

 this prominence, above, is another swelling caused by the coraco- 

 brachialis. On either side of the bicipital prominence is a groove, 

 that on the outer side indicating the position of the cephalic vein, 

 and that on the inner side the position of the basilic vein, brachial 

 artery, and median nerve. External to the bicipital prominence, 

 for a short distance above the elbow, is the prominence formed by 

 the brachio-radialis and extensor carpi radialis longior. At the 

 elbow the internal and external epicondyles of the humerus and 

 the olecranon process of the ulna are to be noted. The internal 

 epicondyle forms a very distinct projection, having an inclination 

 backwards, and behind it, close to the olecranon, is the ulnar nerve. 

 The external epicondyle, which is not well marked, may be felt in 

 Semiflexion of the joint. The olecranon process can easily be felt 

 at the back. In extension of the joint the summit of the olecranon 

 is on the same line with the two epicondyles. When the arm and 

 forearm are placed in the position of a right angle, the summit of 

 the olecranon falls below a line connecting the epicondyles. In 

 extreme flexion of the elbow the summit of the olecranon is anterior 

 to a line connecting the epicondyles. The posterior surface of the 

 olecranon is covered by a subcutaneous bursa. The head of the 

 radius can be felt, in extension of the joint, at the bottom of a de- 

 pression situated at the outer and back part, where it lies just below 



