ANTERIOR CERVICAL TRIANGLE. 1053 



the arrangement of the cervical plexus will be seen, together -with the Origin 

 of the phrenic nerve (p. 636) ; also the spinal accessory nerve emerging from 

 the substance of the sterno-mastoid muscle, and forming connections with 

 the cervical plexus before it disappears beneath the trapezius muscle (p. 

 625). The seven cervical and first dorsal nerves are to be cleaned up to 

 their emergence from the intervertebral foramina, the communicating 

 branches of the sympathetic nerve being preserved if possible (p. 691); and 

 the posterior thoracic nerve and the branch to the rhomboid muscles are to 

 be found (p. 643). 



4. Anterior Triangle and Deep parts of the Neck. Let a dissection of the 

 deep fascia and of the sterno-hyoid and sterno-thyroid muscles be made in 

 the middle line between the larynx and sternum, to exhibit the relations of the 

 trachea as connected with the operation of tracheotomy (p. 888), in particular 

 noticing the position of the innominate artery, the common carotid arteries s 

 the thyroid body, the inferior thyroid veins, and the arteria thyroidea ima, if 

 it be present (pp. 340 and 920). The dissection of the anterior triangle of 

 the neck is now to be proceeded with, by cleaning the whole of the sterno- 

 mastoid, sterno-hyoid and sterno-thyroid muscles, and the anterior belly of the 

 omo-hyoid muscle (p. 191); and in front of the sheath of the great vessels 

 the descendens noni nerve, with its twigs to the three last named muscles, is 

 to be laid bare (p. 626). Let the sheath of the vessels be opened, and the 

 upper part of the common carotid artery exposed, with the pneumo-gastric 

 nerve and internal jugular vein beside it ; mark the place of its division into 

 external and internal carotid arteries, and examine the first part of these two 

 vessels, following the external carotid up to the parotid gland. Let the 

 digastric and stylo-hyoid muscles be cleaned, and the parts be exposed in the 

 submaxillary triangle, viz., the superficial part of the submaxillary gland, the 

 submental branch of the facial artery, and the mylo-hyoid muscle, with the 

 nerve that supplies it (pp. 183 and 608) ; observe also the ninth cranial or 

 hypoglossal nerve lying close to the stylo-hyoid muscle, and dissect out its 

 branch to the thyro-hyoid muscle (p. 627). 



The sterno-mastoid muscle is to be divided about three inches from its upper 

 end, and the superior part is to be dissected quite up to the bone, care being 

 taken not to cut the spinal accessory nerve which pierces it. The sterno-hyoid 

 and steruo-thyroid muscles ought now to be divided near their lower end, the 

 thyroid body dissected, and its form and relations noted. The dissector will 

 then direct his attention to the branches of the external carotid artery ; he 

 will dissect the superior thyroid artery and note its sterno-mastoid branch 

 (already cut), and the hyoid, laryngeal, and crico-thyroid branches ; hewilldis- 

 sect also the commencement of the ascending pharyngeal artery, the occi- 

 pital artery as far as the occipital groove of the temporal bone, the posterior 

 auricular artery, the lingual artery as far as the border of the hyoglossus 

 muscle, and the facial artery as far as the lower jaw (p. 346) ; he will also lay 

 bare the pneumo-gastric nerve as far as convenient, tracing the superior and 

 external laryngeal branches (p. 622). 



In the lower part of the neck, the subclavian artery is now to be examined 

 in the three parts of its course ; and the different relations of the subclavian 

 and common carotid arteries in the first part of their courses on the two 

 sides of the body are to be carefully compared (p. 364). The internal 

 jugular and the subclavian veins, with the branches entering them, are to be 

 dissected, and on the left side the arched part of the thoracic duct descending 

 into the angle of junction of these two veins (pp. 459, 469, and 488). 

 The branches of the subclavian artery are to be displayed, viz., the ver- 



