ORGANS OF THE NECK. 371 



The posterior cornua of the hyoid are a pair of slender 

 rods of bone, about half an inch long, running backwards 

 and outwards from the outer angles of the body of the hyoid, 

 parallel to the angles of the jaw. 



Cut up in the middle line between the halves of the mandible. 

 Notice the paired (submaxillary) glands and press them slightly 

 outwards. Between them is the triangular mass of muscle in 

 which the hyoid lies imbedded, its posterior cornua conspicuous 

 by its iridescence. Just to the outer side of these lies the hypoglossal 



B. The Blood-vessels of the Neck. 



The two most important, on each side, are the following : 



1. The external jugular vein has already been seen (p. 353). 



2. The carotid artery runs forward along the outer border 



of the trachea (see p. 357). 



Clean the carotid artery carefully, taking great care to 

 avoid injuring the nerves which lie close alongside it, and a 

 nerve, the ramus descendens of the hypoglossal, which crosses 

 its ventral surface about the level of the thyroid cartilage. 



C. The Trachea. 



The trachea, or windpipe, is a straight tube running 

 down the neck almost in the middle line. It is only partially 

 exposed at present, but will be seen better in the course of 

 the dissection. Its anterior end, the larynx, which lies 

 almost immediately behind the hyoid, is dilated, and sur- 

 rounded on its ventral and lateral surfaces by the wide 

 thyroid cartilage, which forms a prominent median swelling 

 in the throat, between the rami of the mandible. Behind 

 this is the annular cricoid cartilage, which is wide dorsally 

 and narrow ventrally. Behind the cricoid the trachea narrows 

 slightly, and is strengthened by a series of cartilaginous rings, 

 incomplete along the mid-dorsal line. The trachea runs 

 backwards along the neck, and, entering the thorax, divides 



