122 SURGICAL APPLIED ANATOMY. [Chap. ix. 



the muscle to the back of the pinna, so as to run 

 parallel with the external jugular vein, corresponds to 

 the great auricular nerve ; and a third line, running 

 along the posterior border of the sterno-mastoid 

 muscle to the scalp marks the course of the small 

 occipital nerve. These lines, continued downwards, so 

 as to cross the sternum, the middle of the clavicle, 

 and the acromion, will indicate respectively the supra- 

 sternal, supraclavicular, and supra-acromial nerves. 



The spinal accessory nerve reaches the anterior 

 border of the sterno-mastoid muscle at a point about 

 one inch below the tip of the mastoid process. It 

 emerges from beneath that muscle about the middle 

 of its posterior border, crosses the posterior triangle, 

 and passes beneath the edge of the trapezius at a spot 

 on a level with the spine of the vertebra prominens. 



The phrenic nerve commences deeply at the side 

 of the neck, about the level of the hyoid bone, and 

 runs downwards to a point behind the sternal end of 

 the clavicle. About the level of the cricoid cartilage 

 it lies beneath the sterno-mastoid (which covers it 

 wholly in the neck) about midway between the anterior 

 and posterior borders of the muscle. The brachial 

 plexus can be felt, and even seen in very thin sub- 

 jects. Its upper limits may be represented by a line 

 drawn across the side of the neck from a point about 

 opposite to the cricoid cartilage, to a spot a little ex- 

 ternal to the centre of the clavicle. 



The neck. The skin in the subm axillary region 

 is lax and thin, and is often found of considerable 

 value for making flaps in plastic operations about the 

 mouth. The platysma myoides is closely connected 

 with the skin, and to its action is due the turning-in 

 of the edges of such wounds as are athwart the line 

 of direction of the muscle. The amount of subcu- 

 taneous fat in the cervical region varies in different 

 parts. In the suprahyoid region it is apt to undergo 



