e and Eyes. Ordinarily the muscles of accommodation
adjust themselves easily and quickly; if, however, they do not,
frequent and severe headaches occur as a result of too great muscular
effort toward accommodation. Among young people headaches are
frequently caused by over-exertion of the crystalline muscles. Glasses
relieve the muscles of the extra adjustment, and hence are effective
in eliminating this cause of headache.

An exact balance is required between glasses, crystalline lens, and
muscular activity, and only those who have studied the subject
carefully are competent to treat so sensitive and necessary a part of
the body as the eye. The least mistake in the curvature of the
glasses, the least flaw in the type of glass (for example, the kind of
glass used), means an improper focus, increased duty for the muscles,
and gradual weakening of the entire eye, followed by headache and
general physical discomfort.

119. Eye Strain. The extra work which is thrown upon the nervous
system through seeing, reading, writing, and sewing with defective
eyes is recognized by all physicians as an important cause of disease.
The tax made upon the nervous system by the defective eye lessens the
supply of energy available for other bodily use, and the general
health suffers. The health is improved when proper glasses are
prescribed.

Possibly the greatest danger of eye strain is among school children,
who are not experienced enough to recognize defects in sight. For this
reason, many schools employ a physician who examines the pupils' eyes
at regular intervals.

The following general precautions are worth observing:--

1. Rest the eyes when they hurt, and as far as possible do close work,
such as writing, reading, sewing, wood carving, etc., by daylight.

2. Never read in a very bright or a very dim light.

3. If the light is near, have it shaded.

4. Do not rub the eyes with the fingers.

5. If eyes are weak, bathe them in lukewarm water in which a pinch of
borax has been dissolved.

CHAPTER XII

PHOTOGRAPHY

120. The Magic of the Sun. Ribbons and dresses washed and hung in
the sun fade; when washed and hung in the shade, they are not so apt
to lose their color. Clothes are laid away in drawers and hung in
closets not only for protection against dust, but also against the
well-known power of light to weaken color.

Many housewives lower the window shades that the wall paper may not
lose its brilliancy, tha