CHAP. XXXI.] THEORY OF VOCALIZATION. 439 



be regarded as a stringed instrument, in which the sound depends 

 upon the vibrations produced by the movement of the stretched 

 strings, as a wind instrument in which sounds result from the 

 vibration of the column of air within them, or as a reed instru- 

 ment which developes sound by the vibration of one or more highly 

 vibratile tongues acted on by a current of air passing over them. 



By the mechanism we have described, the vocal chords are placed 

 in a position favourable for the production of sounds by their 

 vibration, and the pitch of the sounds so produced modified. 



Professor Willis showed, that in an ordinary respiration the 

 aperture of the glottis assumed a V form ; and its lips are inclined 

 from each other : the apex of the V i g situated towards the thyroid 

 cartilage. When sound is to be produced, the lips of the glottis are 

 made to approximate each other, and their inner edges become 

 parallel. If now a current of air be forced through the chink, a 

 sound is produced, the pitch of which depends entirely upon the 

 tension of the vocal chords. De Kempelin says, that in the produc- 

 tion of sounds, the lips of the glottis are approximated to the one- 

 tenth or one-twelfth of an inch. The chords in vocalization vibrate 

 throughout their whole length ; but no voice-sounds can be pro- 

 duced by the passage of air through the posterior portion of the 

 chink of the glottis between the arytenoid cartilages. Even when 

 the chords are in contact, sound is produced by the forcible trans- 

 mission of air. 



When the vocal chords are rendered tense, a high note is pro- 

 duced; when they are relaxed, a note of low pitch results. A 

 greater number of sonorous vibrations takes place in the former 

 case than in the latter. It has been shown, that in the case of 

 stretched strings, the pitch of the note varies in direct proportion 

 to the amount of tension, according to the law that the number 

 of vibrations produced by strings of similar length varies in pro- 

 portion to the square-roots of the forces which stretch them. A 

 string stretched by a certain force will produce twice the number 

 of vibrations, if the force be increased four times ; or, if a stretched 

 string is caused to vibrate, and so to produce a certain note, if 

 four times the force be employed, we obtain a note which is the 

 octave of the first, requiring for its production twice the number 

 of vibrations. These results, however, cannot be obtained upon 

 the larynx, so that, as Miiller has proved, the production of vocal 

 sounds in this organ cannot be compared with those produced 

 in a stretched string. 



The distinguished Physician, M. Savart, was among the most 



