THE THOKACIC DUCT IN THE NECK. 1393 



digastric muscle. It crosses forwards, superficial to the occipital and internal and 

 external carotid arteries, immediately below the origin of the superior sterno-mastoid 

 branch of the first-mentioned vessel. The vagus nerve descends vertically, within 

 the carotid sheath, behind and between the carotid vessels and the internal jugular 

 vein ; care must be taken not to include it when ligaturing the common carotid 

 or internal jugular. Surgically, the accessory is the most important nerve in the 

 anterior triangle ; it enters the substance of the sterno-mastoid muscle 1 \ in. below 

 the tip of the mastoid process. A portion of the nerve is resected in the treatment 

 of spasmodic wry-neck, and it' is always exposed in the removal of the medial 

 group of deep cervical glands. The course of the nerve may be mapped out 

 upon the surface by drawing a line from, a point midway between the tip of 

 the mastoid process and the angle of the mandible to a little above the middle 

 of the posterior border of the sterno-mastoid muscle, and thence across the posterior 

 triangle to the anterior border of the trapezius, beneath which it passes at the level 

 of the seventh cervical spine. The deeper guides to the nerve are the posterior belly 

 of the digastric, and the internal jugular vein which it crosses, very obliquely, from 

 above downwards and backwards below and in front of the transverse process of 

 the atlas (felt as a distinct bony landmark midway between the tip of the mastoid 

 and the angle of the mandible). The cervical sympathetic lies in the posterior 

 wall of the vascular compartment of the neck, and may be reached by an incision 

 along the posterior border of the sterno-mastoid : the anterior surfaces of the roots 

 of the transverse processes of the vertebrae are the deep guides to the nerve. 



The cervical plexus, which lies deep to the superior half of the sterno-mastoid 

 upon the leva tor scapulae and scalenus medius muscles, may be exposed through an 

 incision along the posterior border of the upper half of the sterno-mastoid muscle. 

 The phrenic nerve, the most important branch of the cervical plexus, arises one inch 

 above the carotid tubercle and descends almost vertically upon the scalenus anterior ; 

 it is overlapped by the lateral margin of the internal jugular vein. Although fre- 

 quently exposed by the surgeon in removing the lower medial group of deep 

 cervical glands, the phrenic nerve is protected from injury by being covered by 

 the prevertebral fascia. 



The muscular or lower carotid triangle is an important triangular inter- 

 muscular space bounded by the anterior border of the sterno-mastoid, the anterior 

 belly of the omo-hyoid, and the sterno-hyoid. Behind this space, and forming, as 

 it were, its floor, is a still deeper space bounded by the longus colli and scalenus 

 anterior muscles. It may with advantage be termed the prevertebral intermuscular 

 triangle, or, from the fact that it contains the vertebral artery, it may be termed 

 the vertebral arterial triangle. At its apex is the prominent anterior tubercle of 

 the transverse process of the sixth cervical vertebra. By making an incision along 

 the anterior border of the left sterno-mastoid muscle, and passing through this 

 triangle, the surgeon reaches, in order from before backwards, the internal jugular 

 vein, the common carotid artery, the vagus, the thoracic duct, the middle cervical 

 ganglion of the sympathetic, the inferior thyreoid artery, the vertebral vessels, 

 the recurrent nerve, and the oesophagus. The most important bony landmark in 

 this triangle is the prominent anterior tubercle of the transverse process of the 

 sixth cervical vertebra. The common carotid artery may be compressed against 

 this tubercle, which is therefore termed the "carotid tubercle." It is the most 

 important guide to the vertebral artery, which enters the foramen in the transverse 

 process of the sixth cervical vertebra. 



The cervical portion of the oesophagus, which begins at the level of the cricoid 

 cartilage, descends behind, and a little to the left of, the trachea. To expose it, the 

 surgeon, after passing through the above-mentioned muscular triangle, divides 

 the pretracheal fascia, and passes between the trachea and the carotid sheath down 

 to the longus colli muscle medial to the inferior thyreoid artery and vertebral 

 , vessels. The lower pole of the corresponding lobe of the thyreoid gland is retracted 

 medially along with the trachea. The oesophagus lies in the loose cellular tissue in 

 front of the prevertebral fascia ; hence it can be mobilised sufficiently to admit of 

 its being brought to the surface. The oesophagus may also be exposed through an 

 incision in the median plane, the trachea, which is freely movable, being displaced to 



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