SPEECH. 213 



mucous membrane, whilst the movements of the glottis are unaffected. 

 The application of a stimulus to the inferior laryngeal nerve causes 

 contraction of all the muscles, except the crico-thyroid, this muscle 

 alone undergoing contraction when the superior laryngeal nerve is 

 irritated. When the pneumogastric, or its inferior laryngeal branch, 

 is divided, the laryngeal muscles being paralyzed, the arytenoid car- 

 tilages are no longer under muscular control, but, yielding to the cur- 

 rent of air, cause mechanical closure of the glottis, so that the animal 

 dies asphyxiated, unless an opening be made in the trachea. Experi- 

 ments on the spinal accessory nerve show that it also has a certain 

 control over the muscles of the larynx. 



The simple reflex closure of the glottis ta&es place in the case of 

 sudden immersion in a noxious gas, when unaccompanied by sensation. 

 The alternate opening and closing of the larynx, in the act of cough- 

 ing up an irritating body, are sensori-motor movements, being asso- 

 ciated with sensation. The momentary closure of the glottis, when 

 under the influence of emotion or ideas, as in sobbing or laughter, 

 affords examples of emotional or ideational reflex movements. Lastly, 

 the larynx is under the control of the will, as when the glottis is closed 

 by effort, or is variously moved in voluntary coughing, or in the pro- 

 duction of the voice and speech. 



SPEECH. 



Speech, or the utterance of articulate sounds, is a modification of 

 the sounds generated in the larynx, in their outward passage through 

 the cavities of the nose and mouth. Though commonly associated 

 with the production of voice, yet it does not necessarily depend on it; 

 for in whispering, for example, words are articulated simply by the 

 action of the mouth and fauces ; no vocal tones are produced, there 

 being a total absence of laryngeal vibrations, or vocalization, in the 

 act. In whispering, the pitch of the sound varies in different cases, 

 according to the natural pitch of the cavity of the mouth in each per- 

 son. Sighing is another example of the production of sounds by the 

 parts seated above the larynx, totally independent of any action of 

 this organ ; for when the vocal cords also are called into play, the sigh 

 is converted into a groan. The letters of the alphabet, with but few 

 exceptions, may be articulated without, or with only imperfect, laryn- 

 geal action, by drawing in the breath. 



Articulate sounds are divided into vowels and consonants. 



The true vowels, or open sounds, as they are called, are generated 

 in the larynx. They are merely uninterrupted vocal tones, variously 

 modified in their outward passage, by alterations in the shape of the 

 parts of the oral cavity through which they pass; thus, in uttering the 

 pure vocal sounds a, a, e, o, u, pronounced respectively as in the words 

 far, fate, ell, old, and in French words containing the u, one and the 

 same sound produced by the vibrations of the vocal cords is converted 

 into five different sounds, by changes in the position of the tongue, and 

 by the gradual prolongation of the cavity of the mouth, by means of 

 the lips ; the most natural of these vowel sounds, or the one most easily 



