THE HUMERUS 





lateral epicondyle, and separates the antero- 

 lateral from the posterior surface. Its upper 

 half is rounded and indistinctly marked, serv- 

 ing for the attachment of the lower part of the 

 insertion of the Teres minor, and below this 

 giving origin to the lateral head of the Triceps 

 brachii; its center is traversed by a broad but 

 shallow oblique depression, the radial sulcus 

 (musculospiral groove). Its lower part forms a 

 prominent, rough margin, a little curved from 

 behind forward, the lateral supracondylar ridge, 

 which presents an anterior lip for the origin 

 of the Brachioradialis above, and Extensor 

 carpi radialis longus below, a posterior lip for 

 the Triceps brachii, and an intermediate ridge 

 for the attachment of the lateral intermuscu- 

 lar septum. 



The medial border extends from the lesser 

 tubercle to the medial epicondyle. Its upper 

 third consists of a prominent ridge, the crest of 

 the lesser tubercle, which gives insertion to the 

 tendon of the Teres major. About its center 

 is a slight impression for the insertion of the 

 Coracobrachialis, and just below this is the 

 entrance of the nutrient canal, directed down- 

 ward; sometimes there is a second nutrient 

 canal at the commencement of the radial sulcus. 

 The inferior third of this border is raised into 

 a slight ridge, the medial supracondylar ridge, 

 which becomes very prominent below; it pre- 

 sents an anterior lip for the origins of the 

 Brachialis and Pronator teres, a posterior lip 

 for the medial head of the Triceps brachii, 

 < f ,nd an intermediate ridge for the attachment 

 of the medial intermuscular septum. 



Surfaces. The antero-lateral surface is di- 

 rected lateralward above, where it is smooth, 

 rounded, and covered by the Deltoideus; for- 

 ward and lateralward below, where it is slightly 

 roncave from above downward, and gives origin 

 to part of the Brachialis. About the middle 

 >f this surface is a rough, triangular elevation, 

 ;he deltoid tuberosity for the insertion of the 

 eltoideus; below this is the radial sulcus, 

 lirected obliquely from behind, forward, and 

 lownward, and transmitting the radial nerve 

 md profunda artery. 



The antero-medial surface, less extensive than 

 ;he antero-lateral, is directed medialward above, 

 'orward and medialward below; its upper part 

 narrow, and forms the floor of the intertuber- 

 lar groove which gives insertion to the tendon 

 of the Latissimus dorsi; its middle part is 

 slightly rough for the attachment of some of 



Articular 

 capsule 



Articular 

 capsule 



1 Tro ch i 



FIG. 208. Left humerus. Posterior view. 



