The four main functions required for life, namely the digestive, respiratory, circulatory, and excretory systems are all found in plants but performed by different organs. If these functions are non-existent the dynamism or the essence of existence that we call life will disappear and death is inevitable. If these four functions (digestion, circulation, respiration, and excretion) are in working order, it means an organism is alive but only at the level of plant life. To reach the animal level of life, in addition to the four main functions, functions like senses, nervous and muscular systems are also required.
If these functions fail, life continues, but at the level of plant life. We sometimes hear people saying “in a vegetative state.” When you hear this, people are usually talking about a person who has lost the use of the animal functions. He or she may be unable to see, feel, hear, or move. Intelligence, comprehension, will power, conscience and the many other special aspects of human beings cannot be compared with the essential functions of living; these are additional characteristics of being human which accompany the animal system of functions and emerge in relation to a person’s spirituality. This obviously does not mean that those who have lost their abilities are less human and they do not have any rights; on the contrary, it means to say that they are not responsible any more.
The focal points of sensory functions of sight, hearing, touch, taste, and smell are found within the head in the brain, which is the command center of our body and the most complex form of existence we know of in the universe. The brain is connected to the nervous system which communicates with all the organs in the human body. This is why the head is so precious; it is a very sensitive part of the body and has to be protected like a jeweler guards precious stones. If you tread on a nail, it may hurt for a while, but with treatment the wound can be cured. But if a nail were to penetrate someone’s head, this could damage any of the sensory functions or, God forbid, could even result in death.
As you have probably understood from our introduction, the head is firstly the center of animal functions then the focus point of the addition of the human senses. When you mention the head we are the first thing that comes to mind: the eyes. Did we hear you ask why? It’s because we are what you are reading these words with right now, and because you can see the beautiful creations of the universe with us-that’s why.
If my Creator had not created us and positioned us in the two cavities on your head, you would have no knowledge of the beauties of light, color, insects, flowers, roses or birds. You would be afraid to walk without us because you would have no idea where you are about to tread. The effect of sight can only be sent through us to your brain and reflected into your mind. The development of human knowledge would have been very delayed if God had not created us or the other sense organs because the only way to gain knowledge is through healthy sense organs. The sense organs are the only way of detecting and recognizing the characteristics of objects.
You need us to realize that water is transparent, apples are red, quinces are yellow and violets are purple, you need us to recognize your mothers, fathers and friends. You need us to eat, drink, read and write and so you do not bump into walls. What do you think will happen if we close our lids for ten seconds and you try to walk down the street? Try it if you want!
You see-it was harder than you thought. You were scared in case you bumped into something or fell over. Look, Peter, just take a deep breath and give praise to our Creator while our lids are closed tight, for you could not tolerate being in the dark for a mere ten seconds, so what if you never saw the light? Just think sometimes about people who are not as fortunate as you, who cannot see for one reason or another. Give praise to our Creator for not giving you such a trial, and pray for the patience of those friends who have been deprived of sight.
Yes, now we have come to our characteristics and delicate creation, so pay attention. When Darwin saw God’s magnificent skill in our creation, he realized that we could not have been just a coincidence or a self-made creation, and it was impossible for us to be a creation of unconscious nature. Due to the guilt he felt inside, he found it necessary to say that the idea that “the evolution of complex organs like the brain and the eye could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.”
There is no artificial optical device that can match the esthetics or precision of our creation. Our operating principles depend on the optical laws God Almighty has determined for the light. As a matter of fact, just by looking at our structure, human beings worked out the rules of optics, you made the simplest of cameras, and you went on to produce the most magnificent photographic cameras possible. But whatever you do, never try to compare one of us to those cameras you have invented or you may become rather embarrassed. Your cameras are a simple toy compared to us. From the time of the invention of the old, wooden box cameras that had to be covered with a black cloth up to the modern digital cameras of the present, 175 years have passed. Many people worked for years to bring cameras to such a perfect state. Can anyone claim that the old camera made of a wooden box and a lens evolved by itself and turned into the high-quality, digital cameras of today? With all the knowledge accumulated by hundreds of scientists over the years, can this invention really be called a coincidence? So, can we be a coincidence? Could the eyes of mollusks or insects make themselves evolve and transform into the eyes of humans? Of course not! But to understand this a little better you must pay attention to our structure.
We are globe-shaped and look like covered capsules with a multi-layered structure which is quite solid and supple (Figure 1). Each of us is approximately 24mm in diameter. We have an outer layer made of something called sclera (hard coating). We are protected by a strong cover made up of dense ligament fibers, and beneath this is the choroid layer (a layer of blood vessels), where the blood vessels nourishing us go into; this layer covers us completely like a network of vessels. In the middle of the eye is the retina which is a layer of film. It is located in the most precious place where our actual receivers of light reside. There are other layers which each have their own duty beneath these layers, but we won’t go into too much detail.
We each have a main casing that is round and has a dome-shaped surface which slightly protrudes. The center of the hard coating, the cornea, is transparent so that it will allow light to pass through. On the outer part of the transparent area is what they call the white of the eye, and the whole areas seen from the front is covered in a clear membrane (the conjunctiva) with mucus cells. This keeps us lubricated. So as to focus light rays, our cornea section is more curved than other sections. There is a tiny chamber behind this curved front and this is actually where the lens, which separates the main chamber, is found. In the front chamber between our lens and cornea is a transparent liquid, the iris, which gives us our color. The black hole in the center of the iris is called the pupil. The iris, which has a special structure of muscles, works like a curtain contracting and expanding our pupil in response to the brightness of light. If the light is powerful, it contracts to protect the retina from any damage, whereas if the light is dim, the iris expands the pupil to allow more light into the retina.
The fibers (zonules) that hold the lens suspended in place and the cluster of muscles (corpus ciliare), which changes our lens according to the focus distance, are in front of a layer of blood vessels. Our lens, which plays a role in focusing, changes shape and adjusts according to whether the focus point is near or at a distance by thinning and thickening. We do this with the help of the fibers that keep the lens suspended.
Behind the lens is a larger chamber filled with a jellylike, transparent liquid (vitreous humor). The pressure and consistency of the jellylike liquid ensure that we keep our round shape. There are photoreceptive cells in the shape of rods and cones which are sensitive to light in the dark chamber behind our retina. The visual images formed by the rays which pass through the cornea and lens to the retina are upside-down. There is a small pit in my retina where almost every cell has a light receptor cell. This is where your sharpest vision is formed, but that doesn’t mean that it is where you actually perceive the object you are looking at. Sight is what happens when a group of cells in the brain’s visual center is stimulated, and the images on our lens are comprehended. It is unbelievable how fast is the effect of the chemical and electro events on our light receptor cells. The effect of light is conveyed to your brain through the stimulation of electric signals in our receptors’ optic nerve where the actual vision is produced in the brain, so in a way we are just the means of vision.
Because we are such delicate and sensitive organs, our Creator placed us in the cavities within the bone structure of your head for protection. We fit in the very strong and secure structure comprising your chin bone, cheek bones, forehead bone, orbital bone (just around us, your eyes), nasal bone and occipital bone (at the rear and bottom of your skull), but this is not our only protective mechanism. We have top and bottom eyelids that we close to protect ourselves from oncoming dangers. The frequent blinking of our eyelids prevents our cornea from becoming dirty, just like the windscreen wipers of a car. Our eyelids are not just simple folds of skin, they are a secretion system of glands which continuously lubricate the inner part of your lashes and seize dirt and dust, turning them into harmless particles. When you feel emotion, the secretion produced by the tear glands between us and the nose fills the tear ducts, passes through the two canals, and gives us a good wash. But when you cry too much, the excess secretion empties through another canal, which also washes your nose.
As this system is complex, it can also go wrong sometimes. If you consider our many parts and our millions of cells you will clearly see the possibility that any one of our components may fail. However, our Creator has formed the eyes in most people’s heads without any defect or failure, so we can serve you with vision of the universe.
The Creator gives us something called illness so we are reminded of our weakness, a defect or failure which arises as an act of wisdom. Some illnesses, like diabetes, deficiency of vitamin A or atherosclerosis, may have a negative effect on us and even render us useless. We eyes also have some defects which occasionally appear, such as not being able to see at a distance, or close up. Focus defects are easily remedied with spectacles or lenses, but faults in the sensitive light receptor cells in the retina are more difficult to amend. The pressure of the liquid in our larger chamber must be correctly balanced. If this pressure increases too much, we will give you a great deal of pain due to what doctors call glaucoma. If we lose our transparency, your vision will become clouded by what is called a cataract. Apart from this, there are many viruses and bacteria that can cause infections and diseases, but the cells of your immune system are like soldiers who, with the Creator’s help, protect you from those bacteria and viruses.
Look, Peter! It would take pages and pages for us to explain ourselves to you, but we don’t really want to confuse you with even more anatomical information. Our whole aim is to explain the reasons for the creation of our parts, to astonish you with the wisdom and fine art of the Divine, so you will contemplate the wonders of creation and give praise to the Almighty for the blessings he has bestowed upon you. If we have been successful in achieving this, that would be the greatest reward we could ask for.
Irfan Yilmaz is a professor of biology at Dokuz Eylul University, Izmir, Turkey.