76 



HUMERUS ULNA. 



The lower extremity is flattened from before backwards, and is 

 terminated inferiorly by a long articular surface, divided into two 

 parts by an elevated ridge. The external portion of 

 Fig. 29.* the articular surface is a rounded protuberance, 

 which articulates with the cup-shaped depression 

 on the head of the radius ; the internal portion is a 

 concave and pulley-like surface, which articulates 

 with the ulna. Projecting beyond the articular 

 surface on each side are the external and internal 

 condyle, the latter being considerably the longer ; 

 and running upwards from the coridyles upon the 

 borders of the bone are the condyloid ridges, of 

 which the external is the most prominent. Immedi- 

 ately in front of the articular surface is a small de- 

 pression, for receiving the coronoid process of the 

 ulna during flexion of the fore-arm ; and immedi- 

 ately behind it a large and deep fossa, for containing 

 the olecranon process in extension. 



Developement. By seven centres ; one for the 

 shaft, one for the upper extremity, one for the 

 greater tuberosity, one for the rounded protuberance, 

 and one for the trochlear portion of the articular 

 surface, and one for each condyle. 



Articulations. With the glenoid cavity of the 

 scapula, and with the ulna and radius. 



Attachment of Muscles. To twenty-four ; by the 

 greater tuberosity to the supra-spinatus,infra-spinatus, 

 and teres minor; lesser tuberosity, subscapularis; anterior bicipital 

 ridge, pectoralis major ; posterior bicipital ridge and groove, teres 

 major and latissimus dorsi ; shaft, external and internal heads of the 

 triceps, deltoid, coraco-brachialis, and brachialis anticus ; external 

 condyloid ridge and condyle, extensors and supinators of the fore- 

 arm, viz. supinator longus, extensor carpi radialis longior, extensor 

 carpi radialis brevior, extensor communis digitorum, extensor 

 minimi digiti, extensor carpi ulnaris, anconeus, and supinator 

 brevis ; internal condyle, flexors and one pronator, viz. pronator 

 radii teres, flexor carpi radialis, palmacis longus, flexor sublimis 

 digitorum, and flexor carpi ulnaris. 



ULNA. The ulna is a long bone, divisible into a shaft and two 

 extremities. The upper extremity is large, and forms principally 

 the articulation of the elbow ; while the lower extremity is small, 



* The humerus of the right side; its anterior surface. 1. The shaft of the bone. 

 2. The head. 3. The anatomical neck. 4. The greater tuberosity. 5. The lesser 

 tuberosity. 6. The bicipital groove. 7. The anterior bicipital ridge. 8. The posterior 

 bicipital ridge. 9. The rough surface into which the deltoid is inserted. 10. The nu- 

 tritious foramen. 1 1. The rounded protuberance of the articular surface. 12. The 

 pulley-like surface. 13. The external condyle. 14. The internal condyle. 15. The 

 external condyloid ridge. 16. The internal condyloid ridge. 17. The fossa for the 

 coronoid process of the ulna. 



