THE PRODUCTION OF THE VOICE. 537 



cords which bound the glottis, caused by currents of expired air impelled 

 over their edges. If a free opening exists in the trachea, the sound of 

 the voice ceases, but it returns if the opening is closed. An opening 

 into the air-passages above the glottis, on the contrary, does not prevent 

 the voice being produced. By forcing a current of air through the 

 larynx in the dead subject, clear vocal sounds are elicited, 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 glottis may 

 be narrow. 



The vocal ligaments or cords, therefore, are regarded as the proper 

 organs for the production of vocal sounds : the modifications of these 

 sounds being effected, as will be presently explained, by other parts, 

 viz., by the tongue, teeth, .lips, etc. The structure of the vocal cords 

 is adapted to enable them to vibrate like tense membranes, 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. 



Thus it will be seen that the larynx is the organ of voice. It may 

 be said to consist essentially of the two vocal cords and the various car- 

 tilaginous, muscular, and other apparatus by means of which not only 

 can the aperture of the larynx (rima glottidis), of which they are the 

 lateral boundaries, be closed against the entrance and exit of air to or 

 from the lungs, but also by means of which the cords themselves can be 

 stretched or relaxed, brought together and separated in accordance with 

 the conditions that may be necessary for the air in passing over them, to 

 set them vibrating to produce the various sounds. Their action in 

 respiration has been already referred to. 



Anatomy of the Larynx. The principal parts entering into the formation of 

 the larynx (figs. 342 and 343) are the thyroid cartilage ; the cricoid cartilage ; 

 the two arytenoid cartilages ; and the two true vocal cords. The epiglottis 

 (fig. 343) , has but little to do with the voice, and is chiefly useful in protect- 

 ing the upper part of the larynx from the entrance of food and drink in 

 deglutition. It also probably guides mucus or other fluids in small amount 

 from the mouth around the sides of the upper opening of the glottis into the 

 pharynx and oesophagus : thus preventing them from entering the larynx. 

 The false vocal cords and the ventricle of the larynx, which is a space between 

 the false and the true cord of either side, need be here only referred to. 



Cartilages. (a) The thyroid cartilage (fig. 342, 1 to 4) does not form a com- 

 plete ring around the larynx, but only covers the front portion. (&) The 

 cricoid cartilage (fig. 342, 5, 6) , on the other hand, is a complete ring ; the 



