372 DISSECTION OF THE RABBIT. 



about the level of the middle of the heart into the right and 

 left bronchi, which enter the right and left lungs respectively. 



D. 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. The size of the thyroid varies, increasing with the 

 age and maturity of the rabbit. 



E. The Nerves of the Neck. 



Stretch the carotid artery on one side, and spread out the 

 surrounding connective tissue. Note the large nerve running 

 on its outer side the vagus or pneumogastric nerve. In fol- 

 lowing the nerves for the first time, this nerve, the hypoglossal, 

 and sympathetic are alone of importance. A lymphatic gland 

 and duct lie close to the origin of the nerves of the neck, and 

 should not be mistaken for a nerve and its ganglion. 



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

 skull by 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 vertically downwards for about half an 

 inch, and then divides into branches distributed to the 

 sterno-mastoid and other muscles. 



The sterno-mastoid muscle runs from the front end of the 

 sternum to the mastoid process of the skull behind the ears. 

 Turn it back and follow the branches of the nerve to the base 

 of the skull. 



2. The hypoglossal nerve, the twelfth cranial, and the 

 motor nerve of the tongue, is a stout nerve which 

 leaves the skull by the condylar foramina, im- 

 mediately behind the foramen lacerum posterius. 

 Outside the skull it runs downwards and inwards 

 for about half an inch, and then turns forwards, 

 crossing the internal carotid artery near the point 

 of division of the carotid into internal and external 



