THE ANTERIOR PART OF THE NECK 161 



nerve; (15) the first thoracic ganglion of the sympathetic; 

 (16) the ansa subclavia (Vieussenii). 



The scalenus anterior covers the antero-lateral part of the 

 dome, separating it from the subclavian vein, which ends at 

 the medial border of the muscle. Immediately above the 

 vein the subclavian artery crosses the dome, below its apex. 

 The internal mammary artery descends from the subclavian, 

 passes posterior to the subclavian vein, and is crossed, as it 

 lies behind the vein, by the phrenic nerve, which passes in 

 some cases anterior to, and in others posterior to the artery. 

 The costo-cervical trunk ascends from the subclavian and 

 crosses the apex of the dome ; its superior intercostal branch 

 descends, posterior to the apex, between the first intercostal 

 nerve on the lateral side, and the first thoracic sympathetic 

 ganglion on the medial side. The vagus nerve descends 

 anterior to the medial part of the subclavian artery, and, on 

 the right side, its recurrent branch turns round the lower 

 border of the artery ; the ansa subclavia lies to the lateral 

 side of the recurrent nerve. 



PAROTID REGION. 



It is not possible to examine the relations of either the 

 whole of the internal jugular vein or the external carotid 

 artery, or the whole of the cervical portion of the internal 

 carotid, until the parotid gland has been removed, the infra- 

 temporal and submaxillary regions have been dissected, and 

 the posterior belly of the digastric and the styloid process 

 have been detached and displaced forwards. It is important, 

 however, that the internal jugular vein should be retained in 

 position whilst those parts of the dissection are being pro- 

 ceeded with ; the dissector should therefore stitch the sub- 

 clavian vein to the anterior surface of the scalenus anterior, 

 and the lower part of the internal jugular vein to the first 

 part of the subclavian artery, before proceeding to the study 

 and removal of the parotid gland. 



Glandula Parotis. The parotid gland is wedged into a 

 more or less triangular interval, the parotid space, which is 

 bounded anteriorly by the posterior borders of the masseter, 

 the ramus of the mandible, and the internal pterygoid, and 

 postero-medially by the anterior border of the sterno-mastoid, 



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