Fort Worth gazette. [volume] (Fort Worth, Tex.) 1891-1898, 1893-11-02
LIGHT, COLOR AND the eyg.

Extraordinary Differences In the Power %
Nision--somc interesting Experiments.
While the eyesight Of many persons Is
defective, still greater number have eyes
which are unlike each other In seeing power.
In fact, many practically make use of one
eye only; the other, having been originally
little defective, was by degrees called on
for duty less and less and accordingly de-
generated.
One gentleman could see with his right
eye the figures on the face OF clock five.
eighths Of an inch high at IL feet, while he
could SEQ them as clearly with the left eye
only at eight inches distance, and curiously
enough this extraordinary difference in the
powers OF vision OF both eyes was not de
tected by him until he bad reached middle
age Many people are unable to keep one
eye shut and the other open NJ the same
time.
This is especially common with children,
but less frequent with adults, and IL will
be readily understood that in such cases
considerable differences in the powers Of
the eyes may exist without being suspect
cd. Sir John Herschel mentlons tho case
OF an elderly person who by chance made
the unpleasant discovery that he was alto
gether blind in one eye.
Some simple and easily performed ex-
periments give interesting glimpses into
the constitution OF the eye. Go into dark
room with candle, Looking At the wall
which should be Of a uniform dark tint, on
moving the candle up and down close to
the outer side Of one eye, so that the light
falls very obliquely onto II, one OF what
are called "Purkinie's figures will be
seen. This is an appearance OF n celles OF
diyerging and branched red lines on a dark
field, in the interspace of two or three Of
which IL q sort Of cup shaped disk.
These lines are the blood vessels Of tho
retina, and the disk is the yellow spotn or
most sensitive part Of the eye. In the same
situation, looking still at the dark wall and
keeping the eye fixed on one point, hold
the candle at arms length and move it TO
and fro for distance OF about two inches
on level with the point toward which tho
eye is directed aud little to the right or
left OF IT, when faint light may be seen
moving in the opposite direction to theoau-
die and ON the lower side OF the point looked
| at.
This light, II more nearly inspected, Is
seen to be an inverted image OF the candle
fame, equal in size to it, but Very faint,
and il, in fact, the light Of the candle re-
tiected from the lens Of the eye. Other in.
ternal parts Of the eye also reflect some Of
the light that falls into it, but the images
| formed by them are not 80 easily seen.
1t is well known that the pupil contracts
mechanically in bright light and expands
in faint light, but It has been found that
to some extent this change is under thecon
troll of the will. A scientific observer writ.
ing on this subject says that when fronting
window or other light he can make the
pupil expand or contract at the desire OF
any one looking into his eyes,
The pupil is contracted while be steadily
looks at the light, and when he wishes TO
expand it all that is necessary is to take his
attention away from the eye and fix 1t on
some other part of the body without NOV
ing his eyes. This he does, say, by bit
ing his tongue, plnching his arm or in
some such way. The sensitiveness OF the
retina is diminished by this means, and the
pupil dilates. 1t contracts agnin when the
mind is once more recalled TO the eye and
the bright light.-Tit-Bits.