THE HUMERUS. 



113 



ers; it also gives attachment to the fibres of the brachi- 

 alis anticus. The posterior surface of the humerus is 

 divided obliquely by the musculo- 

 spiral groove ; it gives attachment to 

 the triceps muscle. The lower ex- 

 tremity of the humerus is flattened 

 from before backward; it is limited 

 at the sides by the external and in- 

 ternal borders, which terminate in 

 the internal and external epicon- 

 dyles; below these are the articular 

 surfaces for the radius and ulna. The 

 external border is sharp, and serves 

 for the attachment of the supinator 



longus above and the extensor 



muscles below. It terminates in 



the external epicondyle, which is 



the common origin of the extensor 



muscles of the hand and fingers. 



The inner border is sharp, and 



longer than the outer; it terminates 



below in a projecting mass of bone 



called the internal epicondyle, or, 



briefly, the internal condyle; it af- 

 fords attachment to the tendons of 



origin of the flexor muscles of the 



forearm. The anterior surface pre- 

 sents two depressions one, the coro- 



noid depression, the larger, is just 



above the articular surface for the 



ulna, and accommodates the coro- FlG - SS.-THE HUMERUS, 



POSTERIOR SURFACE. 



noid process; the other, the smaller, 



is above the radial head. These two depressions are 



separated by a well-marked ridge of bone. The posterior 



