The silver lance., 1898-08-19

" dark caves havetw
eyes. In many of such animals, how
aver, the eyes have been overgrown by
the skin, 80 that these eyes would be
useless for vision. even II the animal
should come from Its subterranean
Aome to the light of day The same
rs true Of the mole and mouse tribes
Indeed, all the vertebrate animals have
Two eyes. whether they use them or not.
Not all animals have these two eyes
Numerically placed IL the head. ore
On each side. Certain lshe5 which ap-
parently swim on the side. such as the
turbot, have both eyes on the side-tho
Clark side of the head. That this is not
due to a simple twist OF the head was
demonstrated by Professor Steenstrup
more than twenty years ago.
AT times. by what is termed arrested
development animals, and even human
beings, appear as cyclops, or having
one eye only. But w ever Leard of
third eye In man CT Least? And yct
recent researches prove that man and
all vertebrates seem to possess tie ru-
diments of third eye.
This discovery is not only very inter-
esting. but also remarkably instr fctive,
since lhe rudimentary third eye Of man
mas. by one of the most noted philoso-
piers Of modern days, been looked upon
rs being the seat of the SOUL
AS organs by proper use develop in
strength and perfection, so they Lo-
come weak by lack CT use. If for many
generations an organ should remain
without use. its structure in time be-
comes simpler and more imperfect II
such pioccsA continues throughout
ages, the organ. by constant disuse. viii.
become reduced to a mere rudlment o:
what 1t was In the species using the
same. Thus, species Of birds that only
walk and run. but never 1y. have only
rudimentary wings, as the ostrich,
while in the eagle and the alba.ross
the wings are seen In a state of per
lection.
NOW, In closely examining the skulls
" certain lizards. it was found that near
the top Of the head, under the dark,
Opaque skin. and often in the very bone.
an almost perfect eye exists though no
ray of light ever could reach IL.
This eye shows crystalline lens, a
retina of very complex structure, and
an nerve-in fact, all the essential
parts u perfect eye. But being cov-
cred by the Opaque skin of the animal,
1t Is absolutely useless.
II this optic nerve is traced to the
brain. 1t is found to connect the eve
with the so-called pineal gland of the
brain. This pineal gland is, of course.
In no sense of the word a real gland
but definite portion Of the nervous
tissue Of the brain, invariably located
Just back and partly over the cerebrum.
and in front of the rounded brain-mass
which generally is considered to cor
respond to the corpora quadrigemina In
man.
This third eye of the spotted lizard Is
called the pineal eye. on account of the
nerve connection of Its retina with the
pineal gland.
Now, while in certain lizards this
highly developed we is useless because
It Is covered by opaque skin. and in
others even deeply imbedded in bone.
1t would seem probable that in an
earlier stage Of development this pineaI
eye was not rudimentary. but in con.
slant use. A very slight modification
would accomplish this namely, the
~ sAoASpoA oHCy VI tue Skln covering of the
eye. This is exactly the condition of
the normal eyes in reptiles to-day: the
skin covers them. but it is transparent
where it passes over the eye.
In the skulls of some Of the gigantic
reptiles OF the earlier age of this elobe
paleontologists have long ago found a
large, round perforation. Probably thi.
was the socket of the third or pinea;
eye OF the ichthyosaurus. the plesiosau-
rus and the labyrinthodon.
But much more important conclu-
sion must be drawn from this discov-
that in all vertebrates
even including man. the traces of This
third eye remain to-day The pineal
sye of lizards being connected with the
large pineal gland of the sane ~
would sesn that the pineal gland itself
10 but the nerve center of optic thalmus
for this third eye. In all rentilas 49,,
amphibia the pineal gland is large; so
It is also in fishes. ~