CHAPTER V. 



MUSCLES OF THE THORAX— DISSEC- 

 TION OF THE NECK— THE SYMPA- 

 THETIC SYSTEM— THE BRACHIAL 

 PLEXUS AND THE EAR YNX. 



MUSCLES OF THE THORAX. 



Make a median incision through the skin of the 

 thorax along the line of the sternum, and transverse 

 incisions at the shoulders. Dissect off the flaps of skin 

 from the thorax, shoulder, and upper part of the ab- 

 domen. In removing the skin notice the thin skin-mits- 

 cle extending over the posterior and outer portion of the 

 thorax and the abdomen. Retnove the fat and fascia 

 from the thorax, and the group of pectoralis nniscles 

 will be exposed. 



I. Pectoralis Major Muscle. This name is applied 

 to the large muscle arising from the sternum and ribs, 

 and inserted into the humerus. In reality the muscle 

 can be divided into five or more separate divisions or 

 muscles, whose origin and insertion extend along the 

 lines named. The two or three most anterior of these 

 divisions arise from the anterior end of the sternum 

 as far back as the junction of the 3d rib. They form a 

 group of fibres which pass nearly transversely outward 

 to be inserted into the middle and lower third of the 

 shaft of the humerus. Cut across the fibres of this 



