DISSECTION OF THE AKM. 



and of inner 

 head ; 



direction of 

 the fibres ; 



insertion ; 



relations 



Two inter- 



jnusf.ulur 

 septa : 



humerus along a narrow attachment extending from the root of 



the large tuberosity to 

 the spiral groove. The 

 inner head (c), fleshy 

 and wide, arises from the 

 posterior surface of the 

 humerus below the spiral 

 groove, reaching laterally 

 to the intermuscular septa, 

 and gradually tapering up- 

 wards as far as the inser- 

 tion of the teres major. 

 From the different heads 

 the fibres are directed with 

 varying degrees of inclina- 

 tion to a wide common 

 tendon above the elbow. 

 Inferiorly the muscle is 

 inserted into the end of the 

 olecranon process of the 

 ulna, and gives an expan- 

 sion to the aponeurosis of 

 the forearm. Between the 

 tip of the olecranon and 

 the tendon there is some- 

 times a small bursa. 



The triceps is super- 

 ficial, except at the upper 

 part where it is overlapped 

 by the deltoid muscle. It 

 lies on the humerus, the 

 musculo-spiral nerve, the 

 superior profunda vessels, 

 and the articulation of the 

 elbow. On the sides the 

 muscle is united to the 

 intermuscular septa ; and 

 the lowest fibres are con- 

 tinuous externally with the 

 anconeus a muscle of the 

 forearm. 



Action. All the pieces 

 of the triceps combining 

 in their action will bring 

 the ulna into a line with 

 the humerus, and extend 

 the elbow-joint. As the 



long head passes the shoulder it can depress the raised humerus, 



and adduct the arm. 



The INTERMUSCULAR SEPTA should be carefully noticed. They 



FIG. 22. DISSECTION OP THE DORSAL 

 SCAPULAR VESSELS AND NERVE, AND 

 OF THE TRICEPS MUSCLE. 



