REGION OF THE ELBOW. 



281 



flexion. On the posterior surface there is another depression, the olecranon fossa, to 

 receive the olecranon process in extreme extension. The projecting hook-like shape 

 of the median condyle causes it to be more frequently fractured than the 'less promi- 

 nent lateral condyle. The two condyles are readily felt directly beneath the skin and 

 are the only points of the humerus that are really subcutaneous. 



Ulna. The upper extremity of the ulna articulates above with the trochlea of 

 the humerus and on its outer side with the radius. Its upper end is the olecranon 

 process. The posterior portion of this process is called the tip of the olecranon and 

 is continuous with the posterior surface of the ulna, which is subcutaneous. Immedi- 



FIG. 292. Anterior view of bones of right elbow. 



Flu. 293. Posterior view of bones of elbow. 



ately in front of the olecranon is a large hollow, which receives the trochlea. It is 

 called the greater sigmoid cavity. The anterior margin of the cavity is called the 

 coronoid process. On the outer side of the coronoid process is a hollow called the 

 lesser sigmoid cavity, which receives the head of the radius. Fracture of the bone 

 frequently occurs through the narrow portion of the olecranon process into the greater 

 sigmoid cavity. 



Radius. The radius ends above in a flat rounded head. The upper surface 

 of this head articulates with the capitellum. The lateral surface articulates internally 

 with the lesser sigmoid cavity of the ulna. The remainder of the circumference of 

 the head is embraced by the orbicular ligament. Immediately below the head is the 

 constricted neck and bicipital tuberosity. To the posterior half of this latter the 

 tendon of the biceps is attached, but its anterior portion is smooth and provided with 

 a bursa. The head of the radius is subcutaneous posteriorly, but the rest is too much 

 covered by muscles to be readily palpated. 



