630 TEXT-BOOK OF PHYSIOLOGY. 



A cortical representation for phonatory movements also was located in 

 the lower portion of the pre-central convolution, near the anterior border. 

 Stimulation of this area gives rise to marked adduction of both vocal bands, 

 indicating that the representation is therefore 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 sensibility 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, followed by a strong expiratory 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 lowering of the tension of the vocal bands, and a loss of sensibility of the 

 laryngeal mucous membrane. 



