X XXXI.} DISSECTION OF THE LAEYNX. 338 



and remove one half of the thyroid, taking care 

 not to injure any of the muscles. Trace out 

 ■with the finger the outlines of the cricoid carti- 

 lage. Note that 



It forms a complete ring, which in front is 

 narrow, and is covered by the edge of the 

 thyroid, but behind is deep and enclosed on 

 either side by the thyroid. 



5. On the posterior surface of the cricoid note 

 on each side of a central ridge two lamina3 of 

 muscles, the posterior crico-arytenoids ; cut 

 through their attachment to the cricoid, and 

 reflecting them from below upwards note that 

 they are attached above to the external angles 

 of two cartilages, the arytenoid cartilages^ 

 placed on the posterior upper edge of the cricoid 

 cartilage. 



6. Carefully clear away the tissue from the back of 

 the arytenoid cartilages above the cricoid, and 

 observe on the posterior surface of the former 

 the arytenoid muscle ; cutting it through the 

 middle, which in the sheep is frequently ten- 

 dinous, reflect it on either side ; it will be seen 

 to be attached to the back of each arytenoid 

 cartilage ; the posterior surface of the arytenoid 

 cartilage will now be laid bare, and its articula- 

 tion with the cricoid cartilage can be made out. 



7. Looking at the larynx where the thyroid has 

 been cut away, observe the lateral crico- 



