344 DISSECTION OF THE EABBIT 



the heart into the right and left bronchi, which enter the 

 right and left lungs respectively. 



C. The Thyroid Body. 



The thyroid is a soft vascular body, consisting of a pair of 

 lateral lobes at the sides of the anterior part of the trachea, 

 connected by a narrow median lobe, which runs across the 

 ventral surface of the trachea a short way behind the thyroid 

 cartilage. 



D. The Muscles of the Neck. 



A few of the more prominent of the ventral muscles of the 

 neck are alone described here. 



1. The sterno-mastoid muscles are a pair of narrow but 



strong muscular bands, which arise from the 

 anterior end of the sternum, close to the middle 

 line, and run obliquely forwards and outwards, 

 across the front of the neck, to be inserted into the 

 mastoid processes of the skull immediately behind 

 the ears. 



Cut through the right sterno-mastoid close to its origin 

 from the sternum, and turn it forwards. Near its anterior 

 end, note, and carefully preserve, a branch of the spinal 

 accessory nerve, which enters the muscle on its inner side, 

 about half an inch behind the angle of the jaw. 



2. The sterno-hyoid muscles are a pair of broad but thin 



muscular bands, running along the ventral surface 

 of the neck. They arise from the dorsal surface of 

 the anterior end of the sternum, where the two are 

 fused, and run forwards along the neck. A little 

 behind the angle of the jaw, the two muscles diverge 

 slightly from each other, and are inserted into the 

 bases of the posterior cornua 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 



