PRACTICAL CONSIDERATIONS : THE NECK. 



555 



der can then be made out from mastoid to sternum, but is more accentuated below, 

 where the sternal head is salient and sharply defined. This thin posterior border may- 

 be felt vaguely at the upper part, but cannot be seen. At about the lower third it 

 becomes visible and is continued into the broader and flatter clavicular head. The 

 middle of the muscle is seen throughout most of its length as a fleshy, rounded 

 elevation. Over it, and usually plainly visible, is the external jugular vein, running 

 between the platysma and the deep fascia in a line from the angle of the jaw to the 

 centre of the clavicle. In rest the anterior border is still visible. The position of 

 the muscle on the side towards which the head is turned is indicated by a slight 

 furrow in the skin. The muscles partly overlapped by the sterno-mastoid are, from 

 above downward, the splenius, levator scapulae, digastric, omo-hyoid, sterno-thyroid, 

 and sterno-hyoid. 



Fig. 548. 



External jugular vein 



Trapezius 



Acromio-clavicular joint 

 Acromion process 



Greater 



tuberosity 



of liumerus' 



Coracoid. 

 process 



L 



\ 



Submaxillary glana 



Digastric, anterior belly 

 Hyoid bone 



-f — Thyroid cartilage 



Cricoid cartilage 



Lesser supraclavicular fossa 



Suprasternal notch 

 (jugular fossa) 



^ Omo-hyoid, posterior belly 



Supraclavicular fossa 

 Infraclavicular fossa 



Surface markings of neck, from living subject. 



The interval between the sternal and clavicular heads of the muscle is indicated 

 by a slight depression, — the lesser supraclavicular fossa, — and is bounded below by 

 the upper edge of the inner third of the clavicle. Beneath it, about on a line with 

 the sternal end of the clavicle, lie on the right side the bifurcation of the innominate 

 artery and on the left the common carotid artery. 



Between the outer edge of the clavicular head of the sterno-mastoid and the 

 base of the anterior edge of the trapezius is a broad, flat depression, — the supracla- 

 vicular fossa, — which is made very evident by shrugging the shoulders, and across 

 which the posterior belly of the omo-hyoid runs and can often be seen and felt in 

 thin persons, especially during inspiration or when the head is turned towards the 

 opposite side (Fig. 548). The line of the muscle is from the suprascapular notch, 

 slightly ascending to the anterior margin of the sterno-mastoid at a level with the 

 cricoid cartilage and then rapidly ascending to the body of the hyoid. Below its 



