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STUDIES IN PHYSIOLOGY 



out from its dorsal border an anterior projection (which be- 

 comes connected with the hy'oid bone at the base of the 

 tongue) and a posterior process. The two latter processes 

 fit into little sockets in a second cartilage of the larynx, 

 known as the cri'coid (Greek = ring- 

 shaped). The latter surrounds the 

 posterior portion of the larynx and 

 has the form of a signet ring. The 

 flattened part of this band of carti- 

 lage projects anteriorly between the 

 dorsal edges of the thyroid. At- 

 tached to the top, outer corners of 

 this region of the cricoid are two 

 other small pieces of cartilage, each 

 known as a-ryt'e-noid (Greek = ladle- 

 shaped). All of these larynx car- 

 tilages are movable on each other, 

 and this, as we shall see, is a device 

 for regulating the length of the 

 vocal cords and the distance between 

 them. 



The Vocal Cords. The larynx, 

 like the throat cavity and the wind- 



pipe. is lined with mucous mem- 

 Fia. 146. The Larynx and * J 

 Windpipe, Ventral View, brane, which presents an even sur- 



face except in the region near the 

 opening into the throat. Here the 

 lining of the voice box is pushed 

 inward to form two rather thick 

 folds, the vocal cords. The latter 



6, 6' = bronchi. 



c = cricoid cartilage. 



e = epiglottis. 



h = hyoid bone. 

 t, t' = thyroid cartilage. 

 tr = windpipe. 



are not like strings, as their name implies; rather, they 

 look and act much like projecting lips. The ventral end 

 of each fold is attached to the inner surface of the thyroid 

 cartilage, and behind or dorsally each is fastened to one of 

 the arytenoids (Fig. 147). 



During ordinary breathing the two arytenoids are pulled 



