The inner ear contains the nerve of hearing.
3.

The middle ear is separated from the external ear by the drum-head.
The drum-head is connected with the inner ear by a chain of bones.
4.

Sounds cause the drum-head to vibrate.

The ear-bones convey the vibration from the drum-head to the nerve of hearing.
5.

To keep the ear healthy we must avoid meddling with it or putting things into it.
6.