378 DISSECTION OF THE RABBIT. 



already been seen (pp. 347, 376). The dorsal branches of the 

 spinal nerves are easily found, especially in a fresh rabbit 

 The ventral branches are seen traversing the intercostal muscles, 

 and forming the brachial and the pelvic plexus, which can be 

 dissected both down the limb and back to their origin. 



G. The Larynx. 



The larynx, or organ of voice, is the anterior part of the 

 trachea. The thyroid and cricoid cartilages form its outer 

 wall,, and it is protected in front by the epiglottis. 



Make a medium longitudinal section through the anterior 

 part of the trachea. 



1. The epiglottis is a curved plate of cartilage covered by 

 mucous membrane attached to the anterior and 

 ventral border of the larynx. When food is being 

 swallowed it closes over the glottis like a lid, pre- 

 venting the passage of the food into the larynx. 



. 2. The thyroid cartilage forms the most anterior ring of 

 the trachea : it is about half an inch in length along 

 the mid-ventral line, but is incomplete dorsally. 



3. The cricoid cartilage, or second ring of the trachea, is a 



complete ring, lying immediately behind the thyroid. 

 It is narrow ventrally, but wide dorsally ; and 

 articulates with the postero -dorsal angles of the 

 thyroid cartilage. 



4. The arytenoid cartilages are a pair of cartilaginous 



nodules, articulated to the anterior edge of the 

 dorsal surface of the cricoid cartilage. 



5. The vocal cords are a pair of folds of mucous mem- 



brane, strengthened by elastic ligaments. They are 

 attached dorsally to the arytenoids, and at their 

 ventral ends to the thyroid cartilage. It is by 

 their vibration that the ' voice ' is produced. 



6. The glottis is the median slit between the vocal cords, 



through which the air passes to and from the lungs. 



