26 EQUINE ANATOMY. 



or cervical, posterior or dorsal, and inferior or humeral, and three 



borders, anterior, posterior, and superior. 



' The external surface shows two cavities, giving attachment to 



the antea and postea-spinati muscles, divided by a marked crest, 



the spine, running in its long axis; elevated in its middle, the tu- 



berosity. 



The internal surface is concave, forming the sub-scapular fossa 

 for the muscle of the same name. 



The anterior or cervical angle is thin; the posterior thick. 



The inferior or humeral angle has a constricted neck; below 

 this the glenoid cavity, a round, shallow depression, for the humeral 

 head. 



In front of the cavity is the coracoid process, with a base and a 

 summit curved inwardly. 



The superior border is prolonged by a well-marked, flattened 

 cartilage. 



The anterior border is sharp and thin; the posterior, thicker and 

 concave. 



It articulates with the humerus. 



THE ARM. 



The single bone forming the arm is the humerus. 



THE HUMERUS. 



The humerus is a long bone, articulating above with the scapula, 

 below with the ulna and radius. It has a shaft, an upper and a 

 lower extremity. 



The shaft has 

 1 An anterior surface, showing below some muscular imprints. 



A posterior surface, smooth and rounded. 



An external surface, which shows a groove, winding from above 

 downward, and behind forward, called the furrow of torsion, and 

 is bounded in front by an anterior crest, behind by the posterior 

 crest. 



The anterior crest ends below, at the junction of the upper and 

 middle thirds, in the deltoid imprint, a rough and prominent ele- 

 vation, with a concavity toward the furrow of torsion. The 

 furrow of torsion lodges the short flexor of the forearm. 



The internal surface is rounded, and has, at its middle, a rough 

 depression for the teres major and latissimus dorsi. The nutrient 

 foramen is at its lower third. 



