ORGANS OF SPEECH 345 



The arytenoid cartilages are shaped like a triangular pyramid 

 with a curved apex. They rest upon the cricoid cartilage and form 

 with it movable joints having ligaments and synovial membranes. 

 These are gliding joints. They allow the rotation of the arytenoids 

 upon the articular facets of the cricoid. 



The vocal bands are composed of fibrous and muscle tissue 

 covered with mucous membrane. The space between them is 

 the glottis. 



Small muscles, belonging altogether to the larynx, control the 

 position and tension of the vocal bands by their action on the 

 arytenoid cartilages to which the bands are attached, thus 

 producing the different tones of the voice as the breath passes 

 between them. Tense bands and a narrow glottis are necessary for 

 a high note. Lax bands and a wide glottis are the conditions for a 

 low note. 



Above them are two membranous folds, one on either side, 

 formerly called false vocal cords. 



Note. It has been generally taught that the voice is caused by vibrations 

 of the vocal bands, but accurate observations by Miss Alice Groff, of Phila- 

 delphia, and other investigators, have proved that this is not the case, the 

 voice-sounds being like those of a horn rather than a stringed instrument. 



With the aid of lips, tongue, and teeth, the voice sounds are so 

 modified that speech becomes possible, and with it the expression 

 of ideas, and communication between individuals. 



The various air sinuses which communicate with the nasal 

 fossae act as resonance chambers. They give to the voice an agree- 

 able quality of tone, which is in marked contrast to the sound 

 produced when the air current cannot enter these chambers, as in 

 coryza (when the mucous membrane is so swollen as to prevent free 

 admission, to the sinuses, thus causing the nasal tone). 



