476 VOICE AND SPEECH. 



sound of the voice ceases, but returns on the opening being 

 closed. An opening into the air-passages above the glottis, on 

 the contrary, does not prevent the voice being formed. Injury 

 of the laryngeal nerves supplying the muscles which move the 

 vocal cords puts an end to the formation of vocal sounds ; and 

 when these nerves are divided on both sides, the loss of voice 

 is complete. Moreover, by forcing a current of air through 

 the larynx in the dead subject, clear vocal sounds are pro- 

 duced, though the epiglottis, the upper ligaments of the 

 larynx or false vocal cords, the ventricles between them, and 

 the inferior ligaments or true vocal cords, and the upper part 

 of the arytenoid cartilages, be all removed ; provided the true 

 vocal cords remain entire, with their points of attachment, and 

 be kept tense and so approximated that the fissure of the glot- 

 tis may be narrow. 



The vocal ligaments or cord, therefore, may be regarded as 

 the proper organs of the mere voice : the modifications of the 

 voice are effected by other parts as well as by them. Their 

 structure is adapted to enable them to vibrate like tense mem- 

 branes, for they are essentially composed of elastic tissue ; and 

 they are so attached to the cartilaginous parts of the larynx 

 that their position and tension can be variously altered by the 

 contraction of the muscles which act on these parts. 



The Larynx. 



The larynx, or organ of voice, consists essentially of two 

 elastic lips called the vocal cords, which are so attached to 

 certain cartilages, and so under the control of certain muscles, 

 that they can be made the means not only of closing the larynx 

 against the entrance and exit of air to or from the lungs, but 

 also can be stretched or relaxed, shortened or lengthened, in 

 accordance with the conditions that may be necessary for the 

 air in passing over them, to set them vibrating and produce 

 various sounds. Their action in respiration has been already 

 referred to (p. 166), in connection with ordinary tranquil res- 

 piration, and also (p. 182, et seq.) with other respiratory acts, 

 in which the opening or closing of the glottis, or, in other 

 words, the close apposition or separation of the vocal cords, is 

 an essential part of the performance. In these respiratory 

 acts, however, any sound that may be produced, as in cough- 

 ing, is, so to speak, an accident, and not performed with pur- 

 pose. In the present chapter the sound produced by the vibra- 

 tion of the vocal cords is the only part of their function with 

 which we have to deal. 



It will be well, perhaps, to refer to a few points in the auat- 



