RESONANCE. 



391 



parts of the throat with which it comes in contact, the observer 

 touches it to the back of his hand before introducing it. 



The image which is seen (Fig. 214) is reversed i. e., the 

 epiglottis appears in the upper portion of the image, and the left 

 side of the larynx is at the right, as seen by the observer. 



Laryngoscopic Image during Respiration. If the glottis is ex- 

 amined in the cadaver, the separation of the bands is but about 

 1 or 2 mm., while during life, when ordinary or quiet breathing is 

 taking place, the separation amounts to 3 to 4 mm. Nor is there, 

 in most individuals, much difference between ordinary inspiration 

 and expiration as to the width of the opening, although in some 

 the bands do separate a little during inspiration and again 

 approach during expiration. During deep inspiration the width 

 of the rima glottidis may be 1.3 cm. 



Laryngoscopic Image during Voice-production or Phonation. 

 When a tone is produced the vocal bands approach each other and 

 are rendered more tense ; and the greater the tension the higher 

 is the note. Although in the production of a high note the cords 

 are correspondingly approximated, still this does not seem to be 

 essential, while increased tension of the cords is absolutely neces- 

 sary to the production of a more elevated tone. It is claimed 

 that the depression of the epiglottis and its consequent partial 

 covering of the glottis render the tones 

 produced by the vibrating bands lower 

 in pitch, and that the epiglottis also acts 

 as a sounding-board by reinforcing the 

 vibrations of the air-column which im- 

 pinges against it. 



Resonance. This is defined as 

 " A prolongation or reinforcement of 

 sound by means of sympathetic vibra- 

 tion, or the capability of producing such 

 a continued sound" (Standard Diction- 

 ary) : or " The property of a sonorous 

 body that enables it to absorb the vibra- 

 tions of another sonorous body and vi- 

 brate in unison with it" (Wentworth 

 and Hill). 



Bodies which possess this property 

 are resonators, and good examples are 

 resonant boxes, such as the body of a 

 violin, which contain masses of air. 

 The action of a resonator is illustrated 



and explained as follows (Fig. 215) : If a vibrating tuning-fork is 

 held over the mouth of a cylindrical jar, of about 2 inches diam- 

 eter and 12 inches deep, and water is poured in slowly, it will be 

 noticed that as the air-column grows shorter, the sound grows 



FIG. 215. Tuning-fork and 

 cylindrical jar, to illustrate reso- 

 nance (Carhart and Chute). 



