y
concerned in the production of sound.

6. Describe the larynx.

7. Describe the condition of the vocal cords in speaking and in ordinary
breathing.

8. How are sounds differing in pitch and intensity produced by the larynx?

9. How is the sound produced by the vocal cords changed into speech?

10. What parts of the ear are concerned in transmitting sound waves?

11. Give the purposes of the middle ear.

12. Trace a sound wave from a bell to the basilar membrane, and trace the
impulse that it causes from there to the brain.

13. Give the purpose of the Eustachian tubes; of the rods of Corti; of the
semicircular canals.

14. Give directions for the proper care of the ear.

PRACTICAL WORK

*To illustrate the Origin of Sound.*--1. Strike a bell an easy blow and
hold some light substance, as a pith ball attached to a thread, against
the side, noting the result. 2. Sound a tuning fork by striking it against
the table. Test it for vibrations as above, or by letting the vibrating
prongs touch the surface of water. 3. Pluck a string of a guitar or
violin, and find proof that it is vibrating while giving out sound.

*To show the Transmission of Sound.*--1. Vibrate a tuning fork and press
the stem against a table or desk. The vibrations which are reenforced in
this way will be heard in all parts of the room. Now press one end of a
wooden rod, as a broom handle, against the table, and bring the stem of
the vibrating fork against the other end. The vibrations now move down the
stick to the table, from whence they are communicated to the air. Observe
that the sound waves, to reach the ear, must pass through the rod, the
table, and the air. 2. Fasten the tuning fork to a flat piece of cork by
pressing the stem into a small hole in the center. Vibrate the fork and
let the cork rest on the surface of water in a half-filled tumbler on the
table. The sound will, as before, pass to the table and then to the air.
Observe that in this case the vibrations are transmitted by a liquid, a
solid, and by the air. Compare this action with the transmission of sound
waves by different portions of the ear.

*To show Effects of Sound Waves.*--1. Place two large tuning forks of the
same pitch, and mounted on thin boxes for reenforcing their vibrations,
near each other on a table. Vibrate one of the forks for a moment and then
stop it by means of the hand. Observe that the other fork has been set in
vibration. (This experiment does