e, without turning the body? What is the
effect when the eye is fixed on an object that is indistinctly seen?

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933. When the different parts of the eye are not sufficiently convex,
the image is formed beyond the retina, and thus only distant objects
are distinctly seen. This defect is called _long-sightedness_. The
feebleness in the refracting power of the eye may be caused by
disease; but usually it is a consequence of old age, and is remedied
by wearing spectacles with convex glasses.

HYGIENE OF THE ORGANS OF VISION.

934. _The eye, like other organs of the body, should be used, and then
rested._ If we look intently at an object for a long time, the eye
becomes wearied, and the power of vision diminished. The observance of
this rule is particularly needful to those whose eyes are weak, and
predisposed to inflammation. On the contrary, if the eye is not called
into action, its functions are enfeebled.

935. _Sudden transitions of light should be avoided._ The iris
enlarges or contracts, as the light that falls upon the eye is faint
or strong; but the change is not instantaneous. Hence the imperfect
vision in passing from a strong to a dim light, and the overwhelming
sensation experienced on emerging from a dimly-lighted apartment to
one brilliantly illuminated. A common cause of _am-aur-o'sis_, or
paralysis of the retina, is, using the eye for a long time in a very
intense light.

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932. What is short-sightedness? How is the defect remedied? 933. What
is long-sightedness? How is the defect remedied? 934-942. _Give the
hygiene of the organs of vision._ 934. Do the same principles apply to
the use of the eye as to other organs? What is the effect if the eye
is fixed intently on an object for a long time? What results if the
eye is not called into action? 935. Why should sudden transitions of
light be avoided?

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_Note._ Let the anatomy and physiology of the eye be reviewed from
figs. 139 and 143, or from anatomical outline plate No. 10.

936. _Long-continued oblique positions of the eye should be avoided,
when viewing objects._ If the eye is turned obliquely for a long time
in viewing objects, it may produce an unnatural contraction of the
muscle called into action. This contraction of the muscle is termed
_stra-bis'mus_, or cross-eye. The practice of imitating the appearance
of a person thus affected, is injudicious, as the i