Courtesy: Medical Miracles, from Readers Digest 1981.
November.
From the frontiers of science and the far horizons of
personal courage, these stories of medical triumphs and miracles will reaffirm
your faith in the awesome powers of the human spirit. Dramatic victories and
human triumphs.
Selected and edited by the editors of Readers Digest
How does a pin’s-head ball of cells in the course of so many
weeks become a child? Consider the story
of the making of just one individual part: the eye.
The many cells, which make the human eye, have first
executed correctly a multitudinous dance engaging millions of performers in
hundreds of sequences of different steps.
To picture the complexity and the precession of this performance beggars
any imagery I have. It suggests
purposive behavior—not only by individual cells but also by colonies of
cells. And the impression of concerted
endeavor comes; it is no exaggeration to say, with the force of a clef-evident
truth.
The eyeball is a little camera. Its smallness is part of its perfection. But this is a spheroid camera, which focuses
itself automatically, according to the distance of the picture interesting
it. It turns itself in the direction of
the view required. Indeed it is two
cameras finished to one standard so that the mind can read their two pictures
as one. And it is contrived as though
with forethought of self-preservation.
Should danger therein, in a trice its skin shutters close, protecting
its transparent window.
If a craftsman sought to construct a camera, he would turn
for his materials to wood and metal and glass.
If told to use instead of some albumen, salt and water, he certainly
would not even begin. Yet this is what
that staring embryo, a little pin’s-head bud of multiplying cells, not one
ten-thousandth part the size of the eyeball, proceeds to do. The whole structure, with its prescience and
all its efficiency, is produced by out of specks of granular skin cells
arranging themselves as of their own accord in sheets and layers, and acting
damningly on an agreed plan. The magic
juices that make the eye go by the chemical names protein, sugar, fat, salts,
water. Of them 80 percent water. It all sounds like an unskillful, over salted
tale that challenges belief. But to
faithful observation so it is. There is
more yet.
The biconvex lens is made up of cells like those of the skin
but modified to be glass-clear. It is
delicately slung with accurate centering across the path of the light, which
will some months later enter the eye. It
is a preparing in darkness for use in light.
In front of it a circular screen controls, like the iris stop of a
camera, the width of the beam and is adjustable, so that in a poor light more
is taken for the image. In a camera, the
observer working the instrument makes this adjustment. The observer supplies the actual motor
power. In the eye this adjustment is
automatic, worked by the image itself!
Not only must the lens be glass-clear but also its shape
must be optically right. Its two curved
surfaces, back and front must be curved to the right degree, so that light
brought to a focus on the retina and gives there a shaped image. The optician obtains glass of the desired
refractive index and skillfully grinds its curvature in accordance with
mathematical formulae. With the lens of
the eye, a batch of granular skin cells are told to travel from the skin, to
which they strictly belong, and to settle down in the mouth of the optic cup
and arrange themselves in a compact and suitable ball. Next they are told to turn into transparent
fibers, and to make themselves into a sub sphere—a lens of the right size, set
at the right distance between the transparent window of the eye in front and
the sensitive seeing screen of the retina behind. In short, they behave as if fairly possessed.
Furthermore, the lens of the eye, compassing what no glass
lens can, changes its curvature to focus near objects as well as distant when
wanted—for instance, when we read. And
not merely the lens but the pupil—the camera stop—is self-adjusting. All this without our having even to wish it;
without even our knowing anything about it, beyond that we are seeing
satisfactorily.
The lens and screen cut the chamber of the eye into a front
half and a back half, both filled with clear humor, practically water, kept under
a certain pressure to maintain the eyeball’s right shape. The front chamber is completed by a layer of
skin specialized to be glass-clear, and free from blood vessels which, if
present, would throw shadows within the eye.
This living renewed and which has the special chemical power of killing
germs. The skin above and below this
window grows into movable flaps, dry outside like ordinary skin, but moist
inside, which wipe the window clean every minute or so by painting fresh tear
water over it.
The eye’s key structure is the light-sensitive screen at the
back. It receives, takes and records a
continually changing moving picture, lifelong, without change of ‘plate,’
through very walking day. And it signals
its shifting exposures to the brain. It
is nine fold layer of great complexity.
It is, strictly speaking, a piece of the brain lying within the eyeball.
The cells that are at the bottom of the cup become a
photosensitive layer—the sensitive film of the camera. The nerve lines connecting the photosensitive
layer with the brain are not simple. The
human eye has about 137 million separate ‘seeing’ elements spread out in the
sheet of retina. The number of nerve
lines leading from them to the brain gradually condenses down to a little over
a million. They are in series of relays,
each resembling a little brain, and each so shaped and connected as to transmit
duly to the right points of the brain itself each light picture momentarily
formed and ‘taken.’ On the sense-cell
layer the image has, picture like, two dimensions. But the step from this to the mental
experience is a mystery. For it is the
mind which ads the third dimension when interpreting the two-dimensional picture! And it is the mind, which adds color.
The chief wonder of all we have not touched on yet. The eye sends into the cell-and-fiber forest
of the brain throughout the walking day continual rhythmic streams of tiny,
individually evanescent electrical potentials.
This throbbing, streaming crowd of electrified shifting points in the
sponge work of the brain bears no obvious semblance in space pattern to the
tiny two-dimensional upside-down picture of the outside world which the eyeball
paints on the beginnings of its nerve fibers to the brain. But that little picture sets up an electrical
storm. And that electrical storm affects
a whole population of brain cells.
Electrical charges have in themselves not the faintest elements of the
visual—have nothing of “distance,” nor “vertical,” nor “horizontal,” nor
“color,” nor “near, nor “far,” nor visual anything—yet they conjure up all
these. A shower of little electrical
leaks conjures up for me, when I look, the landscape, the castle on the height
of my friend’s face and how distant he is from me.
How explain the building and shaping of the eyeball, and the
establishing of its nerve connections with the right points of the brain? And how explain not the eye but the “seeing”
by the brain behind the eye? This is the
wonder of wonders, familiar even no boredom.
So much with us that we forget it all our time.
