The Wichita daily eagle. [volume] (Wichita, Kan.) 1890-1906, 1894-08-07
THE 6CM 4 " EYE.
rom Popular Science Jews.

I
feet optical instrument, is an express
sion of human vanity or of an expert
/ knowledge OF the anatomy of the eye
and the physiology of Vision; and
have come 10 the conclusion that the
| latter is the more reasonable theory.
The approach to perfection in mod
ern telescopes and microscopes is won
/ derful indeed; but as Psychologists
! have advanced the knowledge of vision,
the so-called imperfections of the eye
| have been steadily disappearing. and
/ even now there is not much to learn.
! Viewed merely as an optical instru-
| ment, an apparatus contained in .
] globe less than an inch in diameter, in
which is produced an image practic-
| ally perfect in form and color, which
can be accurately adjusted almost in
| stantly for every distance from five
| inches to intnity, is movable in every
! direction. has an area for the detection
| of the most minute details and at the
same time a sufficient appreciation of
large objects, is double, but the images
in either eye exactly coinciding, en-
ables US to see all shades of color, esti-
mate distance, solidity, and to some
extent the consistence of objects, the
normal human eye may well be called
perfect. The more, indeed, the eye is
studied in detail the more thoroughly
does one appreciate its perfection as an
optical apparatus.
We receive the impression of single
object, although there are two images
-one in either eye; but it is necessary
that the images be made upon CORE
spending points in the two retina. If
the angle of vision in one eye be devil
Rted even to slight degree by pressing
on one globe with the finger we see
two images. One can appreciate how
exactly these points must correspond
when it is remembered that two rays
of light appear as one only when the
distance between them is one thirty
five hundredth of an inch.
1t is literally true that person may
see and yet not perceive. 1t has hap
pened, in certain injuries of the brain,
that a person sees and reads the words
in book and yet does not perceive
their significance. This is called word
blindness. In a certain portion of the
recognize the fact that we see an OBJ
ject; yet this object conveys no idea.
There are two of these so-called GEN.
tiers of vision, one on either side, and
their action is partly crossed. When
the center is destroyed on one side,
the inner half of one eye and the outer
half of the other eye are blinded.
Further back ii the brain, however, is
a center which enables US to perceive
or understand what is seen.
When this center is destroyed we
see objects and may avoid obstacles in
walking, but persons, words, etc, are
not recognized This center exists
only on the left side of the brain.
An impression, however short, made
upon the retina is perceived. The let
ters on printed page are distinct
ly seen when illumined by an electric
spark, the duration of which is only
forty billionth of second; but the i'm
preston remains much longer. Any
thing in motion appears tor US III a way
quite different from the single impress
sion that we should have from an cleo
tric spark. In picture representing
an animal in motion, as it appears in
al instantaneous photograph, the POI
sitions seem absurd and like nothing
we have ever seen.
In looking at horse in action, the |
impressions made by the different posi- |
lions of the animal run into each other, /
and art should represent as nearly as
possible the sum, or average, of these |
irvoror iS alS hat
pressions are diffused in the retina be- |
yond the points upon waich they are I
directly received. This is called IRA /
diation; and the impression is diffused J
farther for white or ight-colored than .
for black or dark objects. 1t is well .
known that white square looks con-
siderably larger than dark square of .
exactly the same size; or the hands in ,
white gloves look larger than in black
gloves.
The whole question of the apprecia-
ton of colors and color-blindness is
still wrapped in mystery. We know
that some persons can not distinguish
between certain colors, but the reason
of this is obscure. Perfect sight can
exist only when the eye is perfect. The
form and color of objects may be dis
torted so that an inaccurate image is
formed upon the retina, and this
image, however imperfect it may be, is
what is perceived by the brain. In
hearing the case is different.
The waves of sound, if they be con-
Quoted to the internal ear, and II the
nerve of hearing, with its examinations,
be normal, can not be modified in the
course of transmission. Sounds are
always appreciated at their exact
value. except as regards intensi-
ty. Enough has been said about the
eye, l think, TO show that it is perfect
" adapted to all requirements, and
whatever defects it may seem to have,
viewed as an optical instrument, rem
der it more useful to Us than if these