=The Ear.=--The ear is made of three parts called the _outer ear_, the _middle ear_ or _eardrum_, and the _inner ear_. The outer ear is made of a plate of skin and gristle and a slightly bent tube about one inch long. At the inner end of this tube is a thin membrane or _drumhead_. Beyond the drumhead is the cavity of the middle ear about as large as a pea. A chain of three tiny bones stretches from the outer drumhead across this cavity to a tiny _inner drumhead_. Beyond the inner drumhead is the inner ear. [Illustration: FIG. 92.--View of the ear from in front. Three little bones stretch across the middle ear.] The middle ear is kept full of air by means of a tube leading from it to the throat. A cold or other sickness may cause this tube to fill up and make you deaf. The inner ear consists of a sac and four bent tubes filled with a watery fluid. They are also surrounded by watery fluid contained in channels in a bone of the skull. The end of the nerve of hearing is on one of the tubes. =How we Hear.=--Throwing a stone in the water makes waves which move farther and farther outward. In the same way a noise causes waves in the air. These waves pass into the ear tube, strike the outer drumhead, and make it move. This moves the chain of bones in the middle ear so that they cause motion in the inner drumhead. This in moving back and forth makes waves in the fluid of the inner ear which strike on the ends of the nerve of hearing and cause messages to be carried to the brain. =Care of the Ears.=--The ears should not be struck or pulled, as the eardrum is easily broken. Do not put pencils, pins, or anything else in your ears. Wax naturally forms in the ear tube to keep out bugs and flies. The outer part of the tube may be kept clean by wiping it with a moist cloth over the little finger. If you often have earache or a running ear, you should have it examined by a physician. _Neglecting a sick ear may cause deafness._ Some persons are deaf in one ear and do not know it. Test each ear by covering the other one with a heavy cloth and note how far off you can hear the ticks of a watch. =The Nose.=--The nose has a skin-like lining, but it is always kept moist by little glands which give out a watery fluid. The endings of the nerve of smell are in the lining in the upper part of the nose. Two nerves lead from the nose to the brain. When we catch cold, much blood rushes to the lining of the nose and it becomes swollen. It then gives out a thick white mucus. This covers the nerve endings, so that we cannot smell. Smell is of great use in telling us whether our food is good, by helping us to enjoy food with a pleasant odor, and by warning us against bad air.