584 TEXT-BOOK OF PHYSIOLOGY. 



located in the lower portion of the precentral convolution, near the 

 anterior border. Stimulation of this area gives rise to marked ad- 

 duction of both vocal bands, indicating that the representation is 

 also bilateral. 



Faradic stimulation of the inferior laryngeal nerve during slight 

 ether anesthetization gives rise to closure of the glottis; the same 

 stimulation, however, during deeper anesthetization gives rise to 

 opening or dilatation of the glottis, a fact indicating that either 

 the adductor muscles or their nerve' terminals are depressed by the 

 action of the ether before the muscles and nerves of opposite function. 

 The superior laryngeal nerves contain motor fibers for the crico- 

 thyroid muscles. Stimulation of the nerve gives rise to contraction 

 of the muscle and increased tension of the vocal bands. It is believed 

 that these fibers are derived originally from the efferent fibers of the 

 glosso-pharyngeal nerve. The remaining fibers of the superior 

 laryngeal endow the upper portion of the larynx with extreme sen- 

 sibility which to a certain extent protects the air-passages against the 

 entrance of foreign bodies. Irritation of the terminal filaments of 

 this nerve by particles of food, solid or liquid, gives rise to marked 

 reflex spasm of the adductor muscles and closure of the glottis, fol- 

 lowed by a strong expiration blast of air from the lungs by which the 

 offending particles are removed. Division of this nerve on both 

 sides is followed by a paralysis of the crico-thyroid muscles, a lower- 

 ing of the tension of the vocal bands, and a loss of sensibility of the 

 laryngeal mucous membrane. 



