1394 SUKFACE AND SUKGICAL ANATOMY. 



the right side. In opening the oesophagus care must be taken not to injure the 

 recurrent nerve, which ascends in the groove between it and the trachea, and also 

 that the loose submucous cellular interval must not be mistaken for the lumen 

 of the tube. The recurrent nerve must be avoided also in operations connected 

 with the thyreoid gland ; it is most liable to be injured during the application of 

 a ligature to the inferior thyreoid artery, which arches medially in front of the 

 nerve to reach the posterior surface of the gland. 



THE THORACIC DUCT. 



The thoracic duct, after entering the root of the neck between the oesophagus 

 and the pleura, ascends to about an men above the clavicle. At this level it arches 

 laterally behind the lower part of the carotid sheath in front of the vertebral vessels. 

 Great care must therefore be taken not to injure the duct in removing the lymph 

 glands which lie in the loose cellular tissue behind the inferior part of the internal 

 jugular vein, between it and the vertebral vein at the medial border of the scalenus 

 anterior. In addition to those glands a few small lymph glands lie adjacent to the 

 lateral aspects of the cervical portions of the trachea and oesophagus. They receive 

 their afferent vessels from the larynx, trachea, oesophagus, and thyreoid gland. 



POSTERIOR TRIANGLE. 



The roof of the posterior triangle is formed by the general envelope of deep 

 cervical fascia, while the fascia which covers the muscles forming its floor, as weft 

 as that covering the brachial nerve trunks and the subclavian artery, is a lateral 

 continuation of the prevertebral fascia. The lateral deep cervical and supra- 

 clavicular lymph glands are embedded in the cellular tissue between these two 

 layers of fascia. In removing these glands, every endeavour should be made to 

 preserve the motor nerves. The accessory nerve, after entering the posterior 

 triangle at the junction of the superior and middle thirds of the posterior border of 

 the sterno-mastoid muscle, crosses the triangle superficially, and parallel to the levator 

 scapulae. It leaves the triangle by passing under cover of the anterior border of 

 the trapezius, at the junction of its middle and inferior thirds. The lesser occipital 

 nerve curves round the accessory from below upwards, superficially, just at the 

 posterior border of the muscle ; it furnishes, therefore, a useful guide to the position 

 of that important motor nerve. 



The dorsalis scapulae nerve (O.T. nerve to the rhomboids) crosses the triangle, 

 inferior to the accessory, and enters the septum between the levator scapulae and 

 scalenus medius muscles. 



The supra-scapular nerve, is seen arising from the lateral edge of the upper 

 trunk of the brachial plexus, a little above the posterior belly of the omo-hyoid 

 muscle. The loops of the cervical plexus lie under cover of the upper part of the 

 sterno-mastoid muscle, between it and the origins of the levator scapulae and the 

 upper part of the scalenus medius muscles. 



The posterior belly of the omo-hyoid, which forms the superior boundary of 

 the subclavian division of the posterior triangle, passes beneath the posterior 

 border of the sterno-mastoid at a point about one inch above the clavicle. The 

 external jugular vein, usually visible through the skin, runs in a line from the angle 

 of the jaw to the middle of the clavicle ; it is the vessel which is generally opened 

 to relieve the right side of the heart in asphyxia. The lumen of the vein is kept 

 patent where it pierces the fascia of the subclavian triangle ; hence a wound of the 

 vein in that situation is liable to be followed by the suction of air into the circula- 

 tion during inspiration. The third part of the subclavian artery can be compressed 

 against the first rib by pressing downwards and backwards, immediately above the 

 clavicle, a little behind the posterior border of the sterno-mastoid muscle. To map 

 out the course of the subclavian artery in the neck, draw a line, convex upwards, 

 from the superior border of the sterno-clavicular articulation to the middle of the 

 clavicle, the highest part of the arch to reach from J to 1 in. above the bone. To 

 ligature the vessel in the third part of its course, an angular incision is made along 



