206 PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



Structure.*— Aside from the epiglottis, the larynx 

 proper consists of four cartilages, the cricoid, the thyroid, 

 and the two arytenoids. The cricoid is a cartilaginous ring, 



Fig. 132.— Cartilages of the larynx: A, cricoid; B, thyroid; C, arytenoid, 

 with the vocal cord (vc) attached ; a, crico-thyroid articulation. 



which sits directly on the top of the trachea. It is narrow 

 in front and very wide behind (Fig. 132, A). The thyroid is 

 the largest cartilage. Its singular irregular form, which 

 can hardly be described in words, is seen in Fig. 132, B. 

 It is bent on itself in the form of a V, opening back- 

 ward, and the point of the V forms the point of the 

 Adam's apple in front. The arytenoids are two trian- 

 gular cartilages in the form seen in Fig. 132, C. These 

 four pieces are put together in such wise that the lower 

 posterior horns of the thyroid are articulated, i. e., mov- 

 ably attached to the sides of the cricoid low down (a), so 

 that the wide gap between the two arms of the thyroid 

 V, is partly filled up by the cricoid. Now the two aryte- 

 noids sit directly on the top of the cricoid (Figs. 131 

 and t34) between the legs of the thyroid, and thus fill 

 up the wide space more fully. This is the skeleton or 

 framework. The rest of the larynx is made up of 

 muscles, except the most important part of all, which we 

 now proceed to describe. 



* There should be a large model for demonstration of these 

 parts. 



