ing tuning-fork; close both ears, and
observe that the ticking or vibration is heard louder. Unstop one ear,
and observe that the ticking or vibration is heard loudest in the
stopped ear.

Experiment 159. Hold a vibrating tuning-fork on the incisor teeth
until you cannot hear it sounding. Close one or both ears, and you will
hear it.

Experiment 160. Listen to a ticking watch or a tuning-fork kept
vibrating electrically. Close the mouth and nostrils, and take either a
deep inspiration or deep expiration, so as to alter the tension of the
air in the tympanum; in both cases the sound is diminished.

Experiment 161. With a blindfolded person test his sense of the
direction of sound, _e.g._, by clicking two coins together. It is very
imperfect. Let a person press both auricles against the side of the
head, and hold both hands vertically in front of each meatus. On a
person making a sound in front, the observed person will refer it to a
position behind him.

347. Practical Hints on the Care of the Ear. This very delicate and
complicated organ is often neglected when skilled treatment is urgently
needed, and it is often ignorantly and carelessly tampered with when it
should be let alone.

Never insert into the ear canal the corners of towels, ear spoons, the
ends of toothpicks, hairpins, or any other pointed instruments. It is a
needless and dangerous practice, usually causing, in time, some form of
inflammation. The abrasion of the skin in the canal thus produced affords
a favorable soil for the growth of vegetable parasites.

[Illustration: Fig. 143.--Diagram of the Middle and Internal Ear.]

This, in turn, may lead to a chronic inflammation of the canal and of the
tympanic membrane. Again, there is always risk that the elbow may be
jogged and the instrument pushed through the drum-head. There is, of
course, a natural impulse to relieve the itching of the ear. This should
be done with the tips of the fingers or not at all.

The popular notion that something should be put into the ear to cure
toothache is erroneous. This treatment does not cure a toothache, and may
lead to an injury to the delicate parts of the ear. A piece of absorbent
cotton, carefully inserted into the ear, may be worn out of doors, when
the cold air causes pain, but should be removed on coming into the house.

Frequent bathing in the cold water of ponds and rivers is liable to
injure both the ears and the general