326 THE SENSES 



larynx, while the consonant sounds are produced by alterations 

 in the current of air above the larynx, and cannot be pronounced 

 except constantly with a vowel. The current is modified mainly 

 by the tongue and teeth in the formation of linguals and dentals, 

 by the cavity of the nose in case of nasals, and by changes in the 

 shape and size of the oral cavity in the production of other sounds. 

 Nervous Supply of the Larynx. The superior laryngeal 

 branch of the teeth is the sensory nerve, which guards the glottis 

 to prevent the entrance of foreign bodies. Impressions made 

 on the filaments of this nerve are reflected through the medulla 

 and inferior laryngeal branch of the tenth to the muscles which 

 close the glottis. The inferior laryngeal also innervates the 

 muscles that vary the tension of the cords, and the superior laryn- 

 geal keeps the mind informed of the state of these muscles and 

 of the necessity for forced expiration or coughing. 



