The Daily Missoulian. [volume] (Missoula, Mont.) 1904-1961, 1917-02-16
Science Tells Why We
Don't See Upside Down

II OW Is 1t that we see objects right side
i up when the image on the rctina. the
screen ut the back OF the eycball. is upside
down? The question has puzzled anatom-
lists opticians and psychologists. Several
theories have been advanced, but a daring
one has been held recently by DIR. Edward
Anthony Spitzka, living in London.
lie Is an authority on anatomy, the
nervous system and the brain, and ridicules
the common explanation given. in tho
case of vision" says DIR. Spitzka, I'VE do
not notice the inverted image on the
retina.
''rhc mind reaches out and secs the OBJ
ject using the organ of vision and tho
brain rs the instrument. The inverted
Image Is only step In the complicated
process"
TO understand sight we must remember
in the first place that the rctina, upon
which all images are formed, is really
par, of the brain, II sort of outpost. This
Is proved by the development OF the eye
in the embryo Of the unborn child. First
two buds. called the optic viscles. push out
from the primitive brain tube; these
clongntc and their outer ends enlarge until
they come IN contact with their covering ut
the site Of the future eye.
The end becomes followed in a cup.
shaped manner to form the rctna, whilo
the stalk becomes the optic nerve. As tho
brain develops certain parts OF 1t become
like relay station on the line from tho
eye to the cortex OF the brain, where tho
gray matter takes up the sensations and
brings them into relation with impulses
from the skin and the ears, where all sen.
sationS are correlated
The optic nerves are made up Of the
fhers which on running back from the eyes
converge I'm the optic chiasm. where some
Of them cross over to the opposite side.
About two-thrds or ivc-cighths OF tho
iibers of each optic nerve thus cross over.
These are the ibers from the medal or
nasal side of the eye.
The hbcrs from the outer or temporal
side do not cross over. Backwar, from
the chiasm the crossed medal and I'M
crossed lateral Ghcrs run together to form
the optic tracts. These again divide md
&" I" different parts OF the brain. so that
each optic tract Is made up OF the fibers
from the inner side of one eye and tho
outer side of the other.
In invcrtcbratc animals, as Insects and
Holsters, there Is no such crossing over
The inner or nasal parts OF our retinas.
from which the tberS cross over NAV be
likcncd to the panoramic eyes OF the fish.
The outer or temporal parts OF our retinas
from which the tbers do not cross, are
those that look on the sides OF objects and
thus give us stercoScopic vision.
I'VE who with two eyes," writes Dr.
Spitzka, form double retinal image, yet
only under unisuu! circumstances do We
see double 1t will be understood that tho
rctinal image In the left halves together
and In the right halves together are by
virtue of the intercrossing Of nerve nbers
both projected to the left and right half re-.
spcctivcy Of the brain. there to be fused
In Il single image. The impression per-
cclved by the cortcx of the brain Is not In
any way duplicated or mirrored reprodnc-
ton Of that on the retina. There Is an
image In two dimensions, but we are able
to perceive it in terms Of three dimensions.
That IS, we recognize depth as well as that
OF length and breadth"
DIR. Spitzka expresses the opinion that
1t Is because our eyes are movable we are
able t. recognize these three dimensions