THE NECK. 137 



regurgitates. The walls of the veins are thin and, if the fascias happen to be relaxed, 

 fall readily together and thus are difficult to see, and are so adherent to the fascias as 

 not to be readily seized. The surgery of this region requires extreme care and the 

 avoidance of haste. 



Nerves. Lying between the internal jugular vein and the internal and common 

 carotid arteries is the pneumogastric or tenth nerve. It here gives off the superior 

 laryngeal nerve, the internal branch of which enters the larynx through the thyro- 

 hyoid membrane to endow the interior of the larynx with sensation; the external 

 branch goes to supply the cricothyroid muscle. The pneumogastric nerve is fre- 

 quently seen in operations in this region. Its division has not been fatal. 



The hypoglossal nerve winds around the occipital artery and goes forward on the 

 hyoglossus muscle, which separates it from the lingual artery. The descendens hypo- 

 glossi filament leaves the parent nerve as it winds around the occipital artery. It lies 

 on the carotid artery in the form of a loop formed by the addition of branches from 

 the second and third cervical nerves. As it descends on the sheath of the vessels it 

 gives a branch to the anterior belly of the omohyoid muscle. The loop sends 

 branches to the sternohyoid, sternothyroid, and posterior belly of the omohyoid, and 

 if the nerve is divided paralysis of these muscles will occur. The nerve is to be 

 pushed aside when ligating the artery and not included in the ligature. The 

 superficial branches from the cervical plexus which come from the middle of the 

 posterior edge of the sternomastoid muscle and ramify towards the median line, 

 are nerves of sensation, and their division in operative work causes no serious symp- 

 toms, hence they are disregarded. The inframaxillary branches of the seventh or 

 facial nerve supply the platysma. 



Lymphatics. The lymphatics are composed of four sets, a superficial set along 

 the anterior border of the sternomastoid muscle, a deep set accompanying the great 

 vessels, a submaxillary set around and on the submaxillary gland, and a set, two or 

 more in number, beneath the chin. 



The submaxillary gland itself not infrequently enlarges and is difficult to dis- 

 tinguish from an enlarged lymphatic node. All these glands are at times subjected 

 to operative procedures. Fig. 163 shows the submental, submaxillary, and super- 

 ficial set of lymphatics enlarged, as well as the submaxillary gland itself. It is taken 

 from a tuberculous subject. 



The nodes below and behind the jaw become enlarged from diseases affecting 

 the tongue, mouth, and throat as well as from affections of the face and scalp. 



The INFERIOR CAROTID TRIANGLE is limited posteriorly by the lower portion 

 of the sternomastoid muscle, anteriorly by the median line of the neck, and superiorly 

 by the anterior belly of the omohyoid muscle. In this triangle, or reached through it, 

 are the lower portions of the common carotid artery and internal jugular vein, with 

 the pneumogastric nerve between. Anteriorly are the larynx, trachea, thyroid gland, 

 and sternohyoid and sternothyroid muscles. The carotid artery, jugular vein, and 

 pneumogastric nerve lie partly in the triangle but rather under the edge of the 

 sternomastoid muscle. Operations on the air-passages, laryngotomy and tracheot- 

 omy; on the thyroid gland, thyroidectomy; and ligation of the common carotid 

 artery and removal of lymph-nodes are all done in this triangle. The superficial 

 and deep lymphatics accompany the vessels; there are also some in Burns' s space 

 above the sternum. In children, instead of the innominate artery ceasing at the 

 sternoclavicular articulation, it sometimes rises above it and may be wounded in 

 operation on the trachea. The thyroidea ima artery, if present, will lie on the 

 trachea, coming up from the innominate or directly from the aorta. 



POSTERIOR CERVICAL TRIANGLE. 



The posterior cervical triangle has as its base the middle third of the clavicle; 

 its anterior side is the posterior edge of the sternomastoid muscle; its posterior side 

 is the anterior edge of the trapezius; its apex is at the point of junction of these two 

 muscles at the superior curved line of the occiput. It is customary to divide it into 

 two triangles by the posterior belly of the omohyoid muscle. The upper triangle is 

 large and is called the occipital triangle. The lower triangle is small and is called 

 the subclavian triangle. This division by the posterior belly of the omohyoid 

 muscle is not always satisfactory. The muscle runs upward and inward in a line 



