Part 3

links to it, so that when the human needs to move that particular part, the whole mechanism responds splendidly to his desire, which is only possible because of those joints.

Each eye has about 140 receptors for light, called cones and_ rods. The number of cones in each eye is 7 million, and the rods are 130 million. The function of the cones is to receive intense light and colours, while the rods are for faint and moderate light. The cones and rods form the eye’s retina. This retina is a half sphere, located at the back of the eye. If viewed through an ophthalmoscope, it seems very attractive. The retina is overlaid by two spheres, the inner is very rich in blood supply, and the outer is a protective shell called the sclera. The eye’s movement is controlled by six muscles, and the coordination is controlled by the cerebrum, the cerebellum and the medulla. As a result of the activity of the retina, a total of half a million neural fibres transmit the image as colour vision.

It should be added that the retina itself is in ten layers, and that the layer of

cones and rods is just a single layer lying at the deepest level.

An eye afflicted with colour blindness may be partially or totally colour blind. An eye with partial colour blindness can distinguish only two of the three primary colours, with all the derivative colours. It may distinguish red and blue or green; it may distinguish red and green slightly. In the case of total colour blindness the eye does not distinguish any colours; all visible objects of various colours seem to it dark gray, exactly as one sees them in the dark.

Parts of the Eye

The cornea is the front window of the eye; it is a thin film that lies in front of the iris and pupil.

The iris is the layer or tunic that gives the eye its colour, black, hazel, blue, or green. It is a muscular body that lies next to the cornea, and has a hole in its middle called the pupil.

The pupil is the hole that can widen or contract according to the intensity of light, enabled to do so by the muscles of the iris.

The lens is a_ transparent, elastic body, containing transparent liquid, and tied by muscles on all sides, which control the convexness of the lens, so as to form a clear reflection of the image on the retina.

The sclera is an outer layer that protects the eye (the ‘white’ of the eye).

The choroid is a layer that lies next to the sclera, and has blood vessels that nourish the eye.

The retina is the layer next to the choroid. It consists of ten layers that cannot be seen with the naked eye, one single layer of which performs the task of seeing, and consists of 140 million cells, which are of two sorts: 1. The rods which perceive normal light 2. The cones which perceive intense light

The head and its senses

Consider the head and_ the large number of bones that it contains. It is said to contain fifty-five bones, varied in shape, size and function. See how the Almighty has mounted it on the trunk, rather like a rider mounted on his animal. In_ its position above the torso Allah has disposed it in the right place to contain four of the five senses: hearing, vision, smell, taste, and touch; and the site of all perception.

The sense of vision has been placed at the front of the head, so that it functions as a sentry, guard, and pilot for the body. He made each eye of seven layers, each layer with a particular quality, size and function. If any of these layers should be missing, or if it were moved away from its place or its shape, then the eye would stop seeing.

The Lord has supplied in the midst of these seven layers the pupil, a wondrous creation, equal to a lentil grain in size, but capable of engulfing the whole horizon from east to west, and extending its power of vision from the sky to the earth. It plays among the parts of the eye the role of the heart among organs, being their master, while all the layers, eyelids and eyelashes are its servants and guards. Glorified be Allah, the best of creators.

See now the eyes. Observe how the Lord made their exquisite shape and their size, adorned them with the eyelids, to protect and shade them, and to receive harmful things, motes and dust in place of the eyes; how they ward off from them any excess of heat and cold that can cause them harm. Observe how He planted at the edge of the eyelids the eyelashes to adorn and beautify them, and they have other benefits apart from cosmetic purposes. And see how Allah provided them with such marvellous power of vision that spans all the space from sky to earth, that reaches all the stars and planets in the sky. It is such a wonderful thing that this tiny organ should have the capacity to accommodate an image of the skies with all their expanse and extent.

Allah created for man the sense of hearing. The ear is indeed a splendid creation! It performs what is required of it to perfection. The outer ear is made hollow, similar to a shell, so that it may collect sound, and then convey it to the outer ear canal. The outer ear is also important for feeling the movement of any insect so that a human may quickly remove it. It has convolutions, grooves and windings that enable it to catch incoming air and sound, and funnel it to the outer ear canal after softening it. Its particular shape helps to lengthen the way for any

intruding insect, so that it may not reach the outer ear canal before the human has taken notice or woken and then checked its progress. There are also other benefits besides the ones we have mentioned.

One aspect of the wisdom of the Lord is observed in that the semi-liquid substance, the ‘ear wax’, overlaying the external ear canal is of such a bitter taste that an intruding creature is repelled by it, and thus prevented from intruding towards the inner ear — it rather does its best to retreat. In the same way, the eye’s liquid is saline, which has a protective effect — the eye being jelly-like, and so unable to stand adverse circumstances: it would be gravely harmed had it not been for the saline liquid that protects and guards it. In contrast, the mouth’s liquid is made to be sweet and pure, so that it is able to sense the taste of things with precision. Had it had a special flavour, it would have given it to things that enter the mouth. One can notice, for instance, that a_ sick person with a bitter mouth judges unbitter things as bitter. This was put in verse by a certain poet:

He whose mouth is sick and bitter Will find bitter fresh and pure water!

The Almighty mounted the nose on the face, giving it a nice shape and size. He provided it with nostrils, with a barrier that separates them. He made it the site of the olfactory sense, so that the nose can distinguish all smells, fragrant or foul, healthy or obnoxious. It also inhales air that reaches the heart, refreshing it, and nourishing it. The Lord did not give the inside of the nose the windings and twists that he gave the inside of the ear, lest that should check odours and weaken them. The Almighty willed that the nose should be the receptor of waste material that collects in it from the brain, from where it is drained

outside. He willed, in His infinite wisdom, that the nose should be narrower at the top than at the base, since this width at the bottom facilitates the collection of the waste material, so that it may be easily dismissed, and for the nose to inhale all its capacity of air, which ascends some distance before it flows to the heart in a way that does not harm or agitate it. The barrier between the two nostrils is placed by the mercy and wisdom of the Lord, since the nose is a pipe and conduit that receives waste material from the head, but is also the channel for the ascending air: this barrier in the middle protects the inhaled air from being contaminated by the impurity that descends from the head. It will be observed that as the liquid flows down, it occupies one of the nostrils in most cases, leaving the other for breathing; but if it flows through both nostrils, the liquid will be on one side, leaving enough space for the inhaled air. Besides, since the nose, unlike other sense organs like the ears or eyes, is single, wisdom dictates that it should be divided into two channels. Should any mishap hurt one of the two nostrils, or should a disease make it ineffective, the other unhurt nostril can carry on with the job, averting the dire consequences to the body of being without the vital part of the nose. To have two noses on the same face would have been disagreeable, and so the Lord of the Worlds, the best of artisans, disposed that it should be just one nose, with this dual structure that parallels the duality of the ears and eyes.

Muscles of the ciliary body contract

<@ Accommodation Light ray from a close object

\ Inverted image impressed on Retina

Lens left and long

muscles taut Ligament of Ciliary

Accommodation of the eye in response to the proximaty or distance of an object

The lens is a transparent body that, like any lens, refracts light-rays that pass through it, focusing them to

one point, on the Retina in this case. The lens consists of a complex layer of tissues, held in place by the fibres connecting the Retina to the Ciliary body which controls the its shape, so that it can always focus light on the Retina, whatever the distance of the object. This process is called accommodation, The image is represented upside down on the Retina, but the brain soon corrects it.

laste buds in canals Circumvallate Papilla

Taste pore — owards brain

to the taste of substances Receptors that transmit on the tongue nerve impulse

The nose and the sense of hearing

Odour enters the nostril with the inhaled air, and spreads _ in the nasal cavities, where it comes in contact with the hairlike endings (cilia) of the olfactory receptors, which synapse with the olfactory nerve cells, and these latter directly transmit the generated