18 SUPERFICIAL ANATOMY OF THE HEAT) AND KECK. 



opposite the thyro-hyoid space ; the middle thyroid vein crosses the common 

 carotid artery near the level of the cricoid cartilage, and the large inferior thyroid 

 veins pass downwards deeply on the front of the trachea. More superficially placed, 

 and often showing through the skin, are the anterior jugular vein near the middle 

 line, and a communicating branch, frequently of large size, between the facial and 

 anterior jugular veins, lying along the anterior border of the sterno-mastoid muscle. 

 The right and left anterior jugular veins are generally connected by a cross branch 

 .of considerable size at the bottom of the suprasternal notch, close to the upper 

 border of the manubrium, and the lower part of each vein is then directed outwards 

 behind the origin of the sterno-mastoid, so that great care must be exercised, in 

 order not to wound the vessel, in dividing this muscle for the cure of wry-neck. 



The position of the tonsil corresponds externally to a spot slightly above the 

 angle of the jaw. 



Behind the sterno-mastoid muscle, between it and the trapezius, is the inter- 

 muscular space known as the posterior triangle of the neck ; inferiorly, this gives 

 rise to a broad depression, the supraclavicular fossa, in which the omo-hyoid muscle 

 and the brachial plexus may be felt, and in thin persons seen. In the angle between 

 the sterno-mastoid and the clavicle, the third part of the subclavian artery can be 

 felt pulsating, and the circulation in the vessel may be arrested here by pressure 

 directed downwards and backwards against the first rib. The subclavian artery, as 

 it crosses the root of the neck, describes a curve with the convexity upwards, having 

 its inner end behind the sterno-clavicular articulation, its outer end beneath the 

 centre of the clavicle, and its mid-point from half an inch to an inch (1 2'5 cm.) 

 above that bone. The left artery is more deeply placed at first than the right, and 

 does not usually rise so high in the neck. The subclavian vein is placed at a lower 

 level, and is, as a rule, entirely under cover of the clavicle. The pleura and lung 

 ascend above the clavicle into the arch formed by the subclavian artery. The pulsa- 

 tion of the transverse cervical artery may frequently be distinguished a short distance 

 above the clavicle. 



The external jugular vein runs over the surface of the sterno-mastoid muscle in 

 the direction of a line drawn from the angle of the jaw to the centre of the clavicle, 

 and is covered only by the integument and the platysma, the fibres of the latter 

 being nearly parallel to the course of the vein. The distance to which it reaches 

 beyond the posterior edge of the sterno-mastoid below varies considerably. Near 

 the clavicle the vein becomes considerably enlarged, being joined by some branches 

 from the shoulder (transverse cervical and suprascapular), which, with the lower 

 part of the trunk, generally form a more or less dense plexus over the third part of 

 the subclavian artery. 



About an inch (2-5 cm.) below the tip of the mastoid process, the spinal accessory 

 nerve passes beneath the anterior border of the sterno-mastoid ; emerging at, 

 or slightly above, the middle of the posterior border of this muscle, it then 

 continues its oblique course across the posterior triangular space, and sinks beneath 

 the upper border of the trapezius on a level with the sixth or seventh cervical spine ; 

 under the latter muscle, the nerve runs downwards immediately internal to the 

 vertebral border of the scapula. The great auricular and superficial cervical nerves 

 also come out at the posterior border of the sterno-mastoid about the middle of its 

 length, and are thence directed, the great auricular upwards to the ear, and the 

 superficial cervical forwards to the front of the neck. 



For the back of the neck, see p. 27. 



