one
or more confusion-colors be selected, proceed as follows: select as a test
color a skein of pale rose. If the person be red-blind, he will choose
blue and violet; if green-blind, gray and green.

Select a bright red skein. The red-blind will select green and brown; the
green-blind picks out reds or lighter brown.

339. Practical Hints on the Care of the Eyes. The eye is an
exceedingly delicate and sensitive organ. While it is long-suffering, its
endurance has a limit. Like all the other organs of the body, the eyes are
better for moderate and rational use. More than any other organ they
require attention to the general health, as the condition of the skin,
exercise in the open air, good food, and proper habits of daily living.

The tissues of the eyes are peculiarly sensitive to any general influence.
Certain constitutional diseases, like rheumatism, lead-poisoning,
diphtheria, and measles often affect the eyes. Special care should be
taken with children's eyes during and after an attack of measles and
scarlet fever. The eyes of young infants should not be exposed to glaring
lights or to the direct rays of the sun, as when taken out in baby
carriages.

[Illustration: Fig. 136.--Showing the Relative Position of the Lacrymal
Apparatus, the Eyeball, and the Eyelids.

A, lacrymal canals, with the minute orifices represented as two black
dots (puncta lacrymalia) to the right;
B, tendon of the orbicularis palpebrarum muscle; apparently under B is
seen the lacrymal sac. The minute openings of the Meibomian glands are
seen on the free margins of the eyelids.

Below A is seen a small conical elevation, with black dots (the lacrymal
papilla or caruncle).]

Glasses should be worn when they are needed. A failure to do this ususally
causes much unnecessary suffering. It is far from wise to postpone as long
as possible the first use of glasses. The selection and proper fitting of
glasses call for the combined skill of both the physician and the
optician. Obstinate headaches are often caused by defective vision, and
may disappear after discontinuing improper glasses.

The habit of reading, in the cars or elsewhere, the daily paper and
poorly printed books, with their blurred and indistinct type, is a severe
strain on the accommodation apparatus of the eyes. It is a dangerous
practice to read in bed at night, or while lying down in a darkened or
shaded room. This is especially true during recovery from i