THE NECK. 63 



toward the opposite side, and swellings of the visceral column soon lead to pressure symptoms 

 from the adjacent vessels and nerves. 



The skin of the anterior cervical region is firmly adherent to the underlying platysma myoides 

 muscle, the relation being similar to that existing between the skin of the scalp and the occipito- 

 frontalis. The skin consequently follows all of the movements of the platysma and, correspond- 

 ing to the direction of the muscular fibers, may be lifted up in large folds running particularly in 

 the vertical direction. The movability of the skin specially adapts it to the performance of 

 plastic operations. 



The arrangement of the muscles in the anterior and lateral portions of the neck renders 

 possible a regional subdivision which is of practical value in the living subject. The inner 

 margins of the sternocleidomastoid muscles, which converge from the mastoid processes to the 

 upper edge of the sternum, together with the border of the lower jaw, form the anterior cervical 

 region (see Fig. 24). The outer margin of the sternocleidomastoid, the anterior margin of the 

 trapezius, and the upper border of the clavicle bound the lateral cervical region. The anterior 

 cervical region is subdivided into a small suprahyoid, and into a larger infrahyoid region by the 

 hyoid bone and the posterior belly of the digastric muscle (see Fig. 24) ; both of these regions may 

 be further subdivided into a single median region and into a lateral paired region. The sub- 

 mental region lies above the hyoid bone and is bounded upon either side by the anterior belly of 

 the digastric muscle ; to either side of the submental region is found the submaxillary region or 

 triangle (containing the gland of the same name), formed by the lower border of the jaw and the 

 two bellies of the digastric muscle. In the central portion of the infrahyoid region is a small 

 diamond-shaped space between the hyoid bone and the upper margin of the sternum and bounded 

 laterally by the inner margins of the sternohyoid 'and sternothyroid muscles ; this important area 

 is known as the median cervical region. The lateral portion of the infrahyoid region bears im- 

 portant relations to the vessels and nerves of the neck and is called the carotid triangle; it is 

 bounded by the posterior belly of the digastric, by the anterior margin of the sternocleidomastoid, 

 and by the anterior belly of the omohyoid. 



The Carotid Triangle. In the carotid triangle (see Figs. 24 and 25) the pulsations of the 

 common carotid artery may be easily felt at the anterior margin of the sternocleidomastoid muscle 

 at the level of the larynx. The carotid artery may be exposed in this situation by an incision 

 made parallel to the anterior margin of the sternocleidomastoid and the vessel may be ligated 

 through this incision (the point of election, according to Cooper). This most favorable situation 

 corresponds to the level of the anterior tubercle upon the transverse process of the sixth cervical 

 vertebra (the carotid tubercle), which may be felt when the anterior margin of the sternocleidomas- 

 toid muscle has been exposed; it also corresponds to the level of the middle cricothyroid ligament. 

 [The anterior belly of the omohyoid crosses the vessel at the level of the cricoid cartilage. ED.] 

 The common carotid artery ascends from the lower angle of the triangle, frequently concealed 

 beneath the margin of the sternocleidomastoid muscle, and divides into the external and internal 

 carotid at the upper margin of the thyroid cartilage [opposite the lower border of the third cervical 

 vertebra. ED.]. The internal carotid artery is normally covered in the first part of its course by the 

 external carotid. [Strictly speaking, the external carotid in the first part of its course is internal, 

 that is, nearer the median line, and anterior to the internal carotid. ED.] To the outer side of 



