148 PRACTICAL ZOOLOGY. 



2. Along the back of the larynx runs a thick muscular 

 tube, the gullet, with a white lining membrane. 



3. Trim away the muscles and other tissues from the 

 front and sides of the larynx. The large cartilage 

 forming the greater part of the front of the larynx is 

 the thyroid cartilage. 



4. Observe the band of muscle attached to either side of 

 the thyroid cartilage and passing horizontally back 

 around the esophagus. 



Cut away this muscle as completely as possible and 

 entirely remove the gullet. Note that the whitish or 

 yellowish mucous membrane which lines the gullet 

 is continuous with the lining of the larynx. Study 

 now more fully the shape of the thyroid cartilage. 



5. Back of the upper part of the thyroid cartilage, cov- 

 ering the upper end of the larynx, is the arched 

 epiglottis. Feel of it to learn its consistency. Press 

 it upward and forward, then downward and back- 

 ward ; observe that it now covers the entrance to the 

 larynx ; note the position it takes when released. 



6. Just back of the upper angle of the thyroid cartilage 

 find a muscle connected with the base of the epiglot- 

 tis ; pull this muscle to determine what effect its 

 contraction produces on the epiglottis. 



7. Under the thyroid cartilage in front observe a narrow 

 ring of cartilage not much wider than one of the rings 

 of the trachea. Move this up and down to prove that 

 it is distinct from the thyroid. This is the cricoid 

 cartilage. 



8. Observe the sheet of muscle passing from the cricoid 

 to the thyroid. Again move the cricoid toward and 

 from the thyroid ; what does this muscle do ? Cut 



