554 HUMAN ANATOMY. 



Lipoma is frequent ; fibroma and enchondroma are occasionally seen in the 

 region of the ligamentum nuchae ; primary carcinoma is rare. 



Congenital cysts — ' ' hydroceles" — of the neck are found beneath the deep fascia, 

 usually in the anterior triangle and below the level of the hyoid. They may arise 

 from dilatation of the lymphatic vessels, or, as Sutton suggests, they may originate, 

 as do the cervical air-sacs in some monkeys, especially the chimpanzees, by the 

 formation of diverticula from the laryngeal mucous membrane. In any event, they 

 ramify in the various intermuscular spaces, and their complete removal is therefore 

 very difficult. 



Branchial cysts and dermoids are not infrequent. They should be studied in 

 connection with the embryology of the region. 



Congenital tumor of the sterno-mastoid is a condition resulting from either rup- 

 ture of muscular fibres or bruising of the muscle against the under surface of the 

 symphysis during delivery. It may be a cause of torticollis. 



Torticollis — "wry-neck" — maybe due to spasm of the sterno-mastoid either 

 alone or associated with a similar condition of the trapezius, especially the clavicular 

 portion, and often of the scaleni or the complexus. Later there is apt to be second- 

 ary contraction of the deep fascia and of the posterior cervical muscles. Tenotomy 

 of the muscle for the relief of this affection is performed at a level just above its 

 sternal and clavicular insertion. The subcutaneous method has been largely dis- 

 carded in favor of division through an open wound. By the former plan, not only 

 were the anterior, and sometimes also the external, jugular veins endangered, but the 

 cervical space described as ' ' visceral' ' was occasionally opened, and, if infection 

 occurred, with fatal results from septic cellulitis or pleurisy. 



Section of the spinal access.ory nerve may be resorted to when the spasm is 

 limited to the sterno-mastoid and trapezius, or of the posterior primary divisions 

 of the first, second, and third cervical nerves when the posterior muscles are involved. 



Landmarks. — Athough but few organs belong exclusively to the neck, a great 

 many structures of much diversity, and connecting the trunk and head, pass through 

 it. The "landmarks" will therefore be found in relation to different systems, — vas- 

 cular, nervous, etc., — those given here referring chiefly to the muscles and their effect 

 upon surface form. 



The mid-line posteriorly has already been described in its relation to the spines 

 of the cervical vertebrae (pages 146-148). 



On the sides of the neck the platysma, when in action, produces inconspicuous 

 wrinkling of the skin. Its fibres are in a line from the chin to the shoulder. The 

 sterno-mastoid, running obliquely from the skull to the sternum and clavicle, divides 

 each lateral half of the neck into two triangles. The anterior of these is bounded 

 above by the lower border of the inferior maxilla and a line extending from the angle 

 of that bone to the mastoid process ; anteriorly by a straight line between the middle 

 of the chin and the sternum ; posteriorly by the anterior border of the sterno-mas- 

 toid. Its apex is at the middle of the upper edge of the manubrium. The posterior 

 triangle is bounded posteriorly by the anterior edge of the trapezius, the hinder 

 edge of the sterno-mastoid in front, and the middle of the clavicle below. Its apex 

 is just behind the mastoid process. 



It will be seen that by this — the usual — description those structures lying imme- 

 diately beneath the sterno-mastoid would be excluded from both triangles. It is cus- 

 tomary, however, to include the common carotid and internal jugular vein in the 

 anterior triangle, although they are both under cover of the anterior edge of the 

 sterno-mastoid. 



The anterior triangle is divided into three — the superior carotid, the inferior 

 carotid, and the submaxillary — by the digastric muscle and the anterior belly of the 

 omo-hyoid. The posterior belly of the omo-hyoid divides the posterior triangle into - 

 a lower or subclavian and an upper or occipital triangle. The structures included 

 within these various triangles will be described in connection with the vessels, 

 nerves, etc. 



The dividing line between the two main triangles — the sterno-mastoid — can be 

 both seen and felt if, with the mouth closed, the chin is depressed and the skull is 

 rotated towards the opposite shoulder. The thick, prominent, rounded anterior bor- 



