THE SKELETAL SYSTEM 



233 



Included in the visceral skeleton of man are the cartilages of the larynx 

 or "voice-box." The largest and most prominent of the laryngeal 

 cartilages is the thyroid or shield-shaped cartilage. The right and left 

 halves of this cartilage stand at approximately right angles to one another. 

 From its dorsal borders extend paired superior and inferior horns. 



The cartilage immediately below the thyreoid has the shape of a seal- 

 ring and consequently is called the cricoid cartilage. The cricoid expands 

 into a broad lamina on its dorsal or posterior surface. Articulating with 



Fig. 189. — The Heidelberg jaw. (Drawn with the camera lucida from a cast and 

 photographs.) (From Hooton's "Up from the Ape," Courtesy of the Macmillan 

 Company.) 



the cricoid on its anterior surface is a pair of pyramid-shaped arytenoid 

 cartilages, so-called because of their resemblance in section to a funnel. 

 A fifth cartilage supports the epiglottis. 



In addition to these, two small paired cartilages usually occur in the 

 larynx, the comiculate and cuneiform cartilages. The corniculate 

 cartilages lie at the apices of the arytenoids. The cuneiform cartilages 

 are of variable occurrence. The cartilages which support the trachea may 

 also doubtfully belong to the visceral skeleton. They form a series of 

 incomplete rings extending along the trachea. 



The three ear bones are named malleus, incus, and stapes from their 

 fancied resemblance to hammer, anvil, and stirrup. Within the cavity 



