DELTOID MUSCLE. 



243 



the trunk. The limb being raised, the .interior fibres will carry it for- 

 wards, and the posterior fibres will move it backwards. 



When the humerus is fixed as in climbing, the muscle assists in sup- 

 porting the weight of the body, and strengthening the shoulder-joint. 



Dissection (fig. 74). The deltoid is to be divided near its origin, and 

 is to be thrown down as much as the circumflex vessels and nerve beneath 

 will permit. As the muscle is raised a large thick bursa between it and 

 the head of the humerus comes into sight. The loose tissue and fat are 

 to be taken away from the circumflex vessels and nerve ; and the size of 

 the bursa having been looked to, the remains are to be removed. The 

 insertion of the muscle should be examined. 



Fte. 74. 



VIEW OF THE MCSCLKS OF THE DORSCM OF THE SCAP0LA, AND OF THE ClRCCMF I. EX VESSELS 



AND KERVE. (Illustrations of Dissections.) 



Muscles: Arteries: 



A. Supra-sp'.natus. a. Posterior circumflex artery. 



B. Infra-spinatus. b. Branch to teres minor. 



c. Teres minor. c. Dorsal scapular branch of sub- 



D. Teres major. scapular. 



E. Latissimus dorsi. Nerves : 



F. Deltoid. 1. Posterior circumflex. 



G. Triceps (long heail). 2. Its cutaneous offset t> the arm. 



H. Levator anguli scapula?. 3. Branch to the teres minor muscle, 



j. Rhomboideus minor. 

 K. Rhomboideus major. 



Parts covered by deltoid. The deltoid conceals the head and upper 

 end of the humerus, and those parts of the dorsal scapular muscles which 

 are fixed to the great tuberosity. A large bursa, sometimes divided into 

 sacs, intervenes between the head of the humerus and the under surface 

 of the deltoid muscle and the acromion process. Below the head of the 



