354 APPLIED PHYSIOLOGY 



SUMMARY 



1. The larynx is a box of cartilage across which two 



strong bands called vocal cords are stretched. 



2. When the vocal cords are tightened and air is expelled 



between them, a sound called the voice is made. 

 '3. The pitch of the voice will depend upon the tightness 

 and length of the cords. 



4. The intensity of the voice depends upon the force 



with which the air is expired. 



5. The quality of the voice is imparted to it by vibrations 



of the air in the lungs, mouth, and nose. 



6. In speech sounds are modified mainly by the lips and 



tongue. 



7. A man must first hear the sound of speech, and then 



learn to imitate it. Special means must be employed 

 to teach a deaf person to talk. 



8. If the vocal apparatus is overworked or becomes 



inflamed, the voice is injured. 



DEMONSTRATIONS 



150. Procure a larynx from a butcher's shop. Notice the large flat 

 thyroid cartilage, and under it the ring-shaped cricoid cartilage. Notice 

 the white vocal cords passing forward to the lower part of the thyroid. 

 Notice the loose mucous membrane above the vocal cords. Grasp the 

 thyroid cartilage so as to move the cricoid forward and backward, and 

 note how the movements tighten and relax the vocal cords. Notice 

 the muscles which move the larynx. Test the pyramidal cartilages to 

 which the vocal cords are attached. 



151. If possible, get a physician to show the vocal cords in action 

 upon a living person. He will do it by means of a small mirror held 

 in the back part of the mouth. 



152. Have the pupils feel each other's chests while counting one, 

 two, three, and note the marked vibrations. In the same way feel of 



