Blackfoot news. (Blackfoot, Idaho) 1891-1902, 1893-12-23
ODDITIES OF the eve.
Singular Kneefs Of LIxhts asd Coiers on
the Windows OF the seal

Singular Knecfs Of LIxhts asd coiers on
the Windows OF the seal
While the eyesight OF many per-
sons Is defective. q still greater NUM-
Der 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 a
little defective. was BY degrees called
on for duty less and less and less.
and accordingly degenerated One
gentleman is reported who could see.
with his right eye. the figures on the
face OF clock five-eights Of an inch
high at twelve feet. while he could
see them as clearly with the left eye
only Al eight inches distance. and,
curiously enough. this extraordinary
difference in the powers of vision OF
both eyes was not detected by him
until he had reached middle age.
Many people are unable 10 keep
one eve shut and the other open at
the same time This is especially
common with children. but less fire.
Quent with adults, and il viii be
readily understood that in such cases
considerable difference in the powers
Of the eyes may exist without being
suspected. Sir John Herschel men
items the case Of an elderly person
who b. chance made the unpleasant
discovery that he was altogether
blind in one eye.
Some simple and easily performed
experiments give interesting glimpses
into the constitution Of the eye Go
into a dark room with a 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 into it. one
OF what are called ''Purkinje's fig
ures" will be seen. This is an ap-
Pearanee Of a selles OF diverging and
branched red lines on dark field.
in the interspace OF two or three Of
which is a sort OF cup-shaped disc.
These lines are the blOOd-yessels Of
the retiua. and the disc is the '.yel-
low spot 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 70 and
/ fro for distance Of about two inches
on a level with the point toward
/ which the eye is directed and little
to the right or left Of il. when a
faint light may be seen moving in
the opposite direction TO the candle
and on the lower side Of the point
I looked at This light, II more near
/ ly inspected, is seen to be an inverted
/ image Of the candle flame. equal in
size to il, but very faint, and is. in
fact. the light Of the candle reflected
/ 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 so easily seen.
It is well known that the pupil
contracts mechanically in bright
light and expands in faint light; but
| it has been found that TO some ex-
tent, this change is under the con-
troll of the will. A scientific observ-
er. writing on this subject says that
when fronting a window or other
light lie can make the pupil expand
or contract at the desire Of any one
looking into his eye. The pupil is
contracted while he steadily looks at
the light, and when he wishes to ex-
pand it all that is necessary is TO
take his attention from the eye and
fix it upon some other part Of the
body without moving the eyes This
he does, say, by biting his tongue,
pinching his arm, or in some such
way. The constituencies Of the retina
is diminished by this means and the
pupil dilates. 1t contracts again
when the mind is once more recalled
to the eye and the bright light.