334 DISSECTION OF THE EABBIT 



behind the angle of the jaw, the two muscles diverge 

 slightly from each other, and are inserted into the 

 bases of the posterior oornua of the hyoid. Their 

 hinder ends are covered by the sterno-mastoids. 



3. The stylo-hyoid muscles are a pair of short muscles, 



running almost transversely across the neck, opposite 

 the angles of the jaws. They arise from the under 

 surface of the tympanic bullae, close to the insertions 

 of the stylo-mastoid muscles, and are inserted into 

 the tips of the posterior comua 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 exoccipital bone by 

 long thin tendons, which run 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 into the inner surface of 

 the ramus of the mandible, close to the symphysis. 



5. The stemo-tliyroid muscles are a pair of thin bands of 



muscle, lying immediately dorsal to the stemo-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 stemo-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 a/rtery ca/refully, taking great care to 

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

 nerve which crosses its ventral surface about the level of the 

 thyroid cartilage. 



