371 



Arc the different modifications of which the voice is susceptible, de- 

 pendent on the width or straightness of the glottis, or on the tension or 

 relaxation of the ligaments forming its sides ? Must we believe with Do- 

 dart, that the larynx is a wind instrument, or, with Ferrein, that it is a 

 stringed instrument ? N 



It is very true that the voice becomes stronger, fuller, and passes from 

 the acute to the grave, as the glottis enlarges with the progress of age 5 

 that it remains always weaker and sharper in a woman, whose glottis is 

 nearly a third smaller than a man's ; but the tension or relaxation of the 

 ligaments, which form the sides of the glottis, (the vocal strings of Fer- 

 rein) may they not enable these ligaments to execute, in a given time, vi- 

 brations more or less prolonged, and more or less rapid, in such a man- 

 ner, that if the air, expelled from the lungs by expiration, strike upon 

 them in the state of tension, produced by the action of the crico-aryte- 

 noidei postici, which carry back the arytenoidal cartilages to which the 

 ligaments of the glottis are attached, whilst the thyroid cartilage, to 

 which are attached the other extremities of the same ligaments, is carried 

 forward by a sort of tilting, occasioned by the muscles connecting it with 

 the cricoid cartilage, (crico-thyroidei)* the voice will be shrill, that is, 

 clear and piercing ; whereas it would be grave, if the arytenoid cartila- 

 ges being brought forward by the action of the crico-ayrtenoidei obliqui, 

 and the thyro-arytenoidei muscles, (the vocal strings being relaxed,) exe- 

 cuted less frequent vibrations. 



It has been objected to Ferrein, that to perform the office of vibrating 

 strings, the ligaments of the glottis are neither dry, nor tense, nor insu- 

 lated, the three-fold condition required for the production of sound, in 

 the instruments to which this anatomist has compared the larynx $ but 

 for all the incompleteness of their resemblance to strings, the ligaments 

 of the glottis, similar to\he vibratory bodies, serving as mouth-pieces to 

 wind-instruments, such as the reed of the oboe, the mouth-hole of flutes, 

 the lips themselves in the horn, do not the less contribute to the form- 

 ation and varied inflexions of the vocal sound. It is the more difficult 

 to set aside their influence altogether, inasmuch as their state of tension 

 coincides always with the contraction of the glottis, and the two condi- 

 tions producing the same effect, it is difficult to determine if it be due to 

 one rather than the other, as it is impossible to decide whether it be to 

 the enlargement of the opening, or the relaxation of the ligaments, that 

 the grave tones are owing. A last reason, which, I think, should make 

 the larynx be considered as serving at once the purposes of a wind and a 

 stringed instrument, is, that the ligature or section of the recurrent nerves, 

 which give to its muscles their contractility, takes away the voice ; so 

 that there is evidently required some kind of action in the sides of the 

 opening. 



When we wish to speak low, we contract but slightly, or not at all, the 

 muscles of the larynx, whose action is entirely under the direction of the 

 will. The column of air meeting, then, in its passage along the glottis, 

 only relaxed parts, and little capable of vibration, the vocal sound is no 

 longer produced. The permanent extinction of the voice, must depend, 

 in most cases, on palsy of the vocal orlaryngeal muscles. 



* The arytenoid. muscle is used in the formation of acute sounds* for btiiiging togeth. 

 <?r the two arytenoid cartilages.- Copland, 



