The Hawaiian star. [volume] (Honolulu [Oahu]) 1893-1912, 1894-05-29
Luerr, COLOR AND THE EYE.
E,trnordinnr, ninerence- Iu the Power of
vision some intcrc.tiug Experiments.

E,traordinnr, ninersnce- In the Power of
vision some Interesting Experiments.
While the cyc.Ilht of many person. Is
defective, % still greater number have eyes
which 1ry Uulikreuph D.hrr Zoo seeing power.
In fact, many practically mike uae OF one
eye only; the other having been originally
q little dvl,c' .rc wa. by degrees allied on
for duty less and lr-, and accordingly de-
generated.
one gentleman could soc with his right
rFe the figures on the face OF % lock FIVE
sh.I- of uu inch high no o. feet while he
-Hu them as clearly With the left eye
tt eight inches distance, and Curiously
uEu this extraordinary difference 10 the
/ POWERS Of vision Of both eyes was not de
] t,cted boy him until be had reached middle
age. Many people are unable 10 keep one
eye shut and the other open st the same
time.
/ This IL 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
ed. Sir John lIer-chel mentions tine 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 theeye 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, 80 that the light
/ falls very obiiquoly onto IL, one VI what
are called "Purkinjc'- figures" will be
seen. This is an appearance of a celles Of
/ diverging and branched red lines on "A dark
field, in the interspace Of two or three of
which is a sort OF cup shaped disk
These lines are the blood vessels of the
retina, and the disk is the yellow spot or
most sensitive part of the eye. In the same
/ situation, looking still at hedark wall and
| keeping the eye fixed on one poiut. 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 the
eye is directed aud "A little 20 the right or
| left of it, when a faint light may be seen
moving in the opposite direction to the can
die and ON the lower side of the point looked
at.
This light, If more nearly inspected, is
seen to be AN inverted image of the candle
flame, equal In size to it, but very faint,
and il, in fact, the light Of the candle re-
fected 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.
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 he con
troll of the will. \ scientific observer writ
| ing on this subject says that when fronting
IA 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 he steadily
| looks at the light, and when he wishes to
/ expand it all that is necessary is tut3tSe his
attention away from the eye and hs it on
/ some other part of the body withou, NOV
/ ing his eyes. This he does say, rs bit
/ ing his tongue, pinching his arm or in
/ some such way. The seusitiveness # tue
retina is diminished by this means, ID the
pupil dilates. 1t contract again wi n the
mind is once more recalled to the e and
the bright light. Bits