MUSCLES AND NERVES OF THE NECK 345 



of the stemo-mastoid muscles, and are inserted into 

 the tips of the posterior cornua of the hyoid. 



4. The mandibular muscles are a pair of slender muscles, 

 triangular in shape, which arise from the tips of the 

 par-occipital processes of the ex-occipital bones by 

 long thin tendons, running forwards and inwards, 

 dorsal to the stylo-hyoid muscles, and parallel to the 

 rami of the mandible. The anterior part of each is 

 muscular, and is inserted iato the inner surface of 

 the ramus of the mandible, close to the symphysis. 



6. The sterno-thyroid muscles are a pair of thin bands of 

 muscle, lying immediately dorsal to the sterno-hyoid 

 muscles, and seen on dissecting along the outer 

 borders of the latter. They are fused posteriorly, 

 and arise from the sternum as a median band in 

 common with the sterno-hyoid: further forwards the 

 muscles diverge, and run along the ventral surface 

 and sides of the trachea, to be inserted into the sides 

 of the thyroid cartilage. 



E. 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. 



2. The carotid artery runs forwards along the outer borders 



of the sterno-hyoid and sterno-thyroid muscles. 



Clean the carotid artery carefully, taking great care to 

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

 nerve tvhich crosses its ventral surface about the level of the 

 thyroid cartilage. 



F. The Nerves of the Neck. 



Sxpose and clean the following nerves on either the right 

 or the left side of the neck. 



1. The spinal accessory nerve, the eleventh cranial nerve, 

 leaves the skull at the foramen lacerum posterius, 

 between the auditory capsule and the ex-occipital 

 bone, in company with the pneumogastric and glosso- 

 pharyngeal nerves. Outside the skull it runs almost 



