The Hand​—‘The Most Elegantly Skillful Organ’

IT WAS an emergency. A young girl lay in the hospital entranceway, the main artery in her right leg having been severed in a motorcycle accident. No surgical instruments were on hand to stop the blood pumping out of the wound. What could the doctor do?

“I used my hand as a clamp,” recalls Professor Napier in his book Hands, “pinching off the artery with thumb and fore-finger as well as I could. Finally I got a bit of string, all that was available, round the artery and tied it off. The blood stopped pumping. . . . Nothing but the hands could have dealt with that emergency so quickly and effectively. Few patients . . . ever realise how, during an operation, an appropriately placed finger has saved their lives.”

Actions like these would be impossible were it not for the saddle joint of the thumb. (See illustration.) Its design allows almost as much movement as the ball-and-socket joint of the shoulder, but unlike the latter, the saddle joint does not need support from a surrounding mass of muscles. The thumb, therefore, can perform delicate movements as it meets the fingertips.

Try picking up a small object or even turning the pages of this magazine without using your thumb. Said a South African doctor: “I have put plenty of injured thumbs in splints, and when the patients come back, they usually tell me they didn’t realize how much they needed their thumb.”

The human hand with its opposable thumb is a remarkably versatile tool. Without the hand, how would you write a letter, take a photograph, hammer a nail, use a telephone, or thread a needle? Thanks to the hand, pianists play exquisite pieces, artists paint beautiful pictures, and surgeons perform delicate operations. “The apes, having short thumbs and long fingers, are handicapped in relation to delicate manual dexterity,” states The New Encyclopædia Britannica.

There is another important difference between the hand of a man and that of an ape. About a quarter of the motor cortex in the human brain is devoted to the muscles of your hands. The human motor cortex, explains Professor Guyton’s Textbook of Medical Physiology, “is quite different from that of lower animals” and makes possible “an exceptional capability to use the hand, the fingers, and the thumb to perform highly dexterous manual tasks.”

In addition, neurosurgeons have discovered another region of the human brain that they call “an area for hand skills.” Skillful hands require sense receptors. These tiny nerve endings are abundant in the human hand, especially in the thumb. A doctor interviewed by Awake! said: “When people lose even a bit of sensation from the tip of their thumb, they find it difficult to position small objects like screws.” Your arms have other types of sense receptors that enable you to move your hands to the right place even in pitch-darkness. Thus, while lying in bed at night, you can scratch your nose without punching your face.

Even a simple act like reaching out for a glass of water is something to wonder at. If your grip is too weak, you may drop the glass. If your grip is too strong, you may break it, cutting your fingers. How do you manage to hold it with just the right pressure? Pressure receptors in your hand send messages to your brain, which sends back appropriate instructions to muscles in your outstretched arm and hand.

Soon, without your having to look, the glass comes to rest gently against your lips. Meanwhile, your attention may be fixed on a television program or a conversation with friends. “The fact that the glass is raised to the lips without being smashed into the face,” states Dr. Miller in his book The Body in Question, “is a tribute to the subtle weighing abilities of the outstretched limb. And the fact that the glass remains at the mouth while losing weight as it is emptied shows how punctually the news is updated.”

No wonder the human hand has caused thinking people to marvel! “In the absence of any other proof,” wrote the famous scientist Sir Isaac Newton, “the thumb alone would convince me of God’s existence.” “We can land men on the moon,” says Professor Napier, “but, for all our mechanical and electronic wizardry, we cannot reproduce an artificial fore-finger that can feel as well as beckon.” Man’s hand, states The New Encyclopædia Britannica, is probably “the most elegantly skillful biological organ” and one that “distinguishes him from all other living primates.”

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The saddle joint of the thumb is unique when compared with the corresponding joints of the fingers

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The human hand with its opposable thumb is a remarkably versatile tool

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Sense receptors in your hand and arm enable your brain to orchestrate complex actions

The Eye​—“The Envy of the Computer Scientist”

THE retina is a small membrane that fits over the back of the eye. As thin as paper, it contains over a hundred million neurons arranged in different layers. “The retina,” states the book The Living Body, “is one of the most remarkable pieces of tissue in the human body.” It is “the envy of the computer scientist, performing approximately 10 billion calculations every second,” states Sandra Sinclair in her book How Animals See.

As a camera focuses an image on photographic film, our eye focuses on the retina an image of what we see. Yet, as Dr. Miller explains, camera film “does not even begin to compare with the versatile sensitivity of the retina.” With the same “film” we can see by moonlight or in sunlight 30,000 times more intense. Furthermore, the retina can discern fine details of an object part of which is bathed in light and the rest of which is in shadow. “The camera,” explains Professor Guyton in his Textbook of Medical Physiology, “cannot do this because of the narrow critical range of light intensity required for proper exposure of film.” Hence, photographers need flash equipment.

The “versatile sensitivity of the retina” is due, in part, to 125 million rods. These are sensitive to small amounts of light, making vision possible at night. Then there are about 5.5 million cones that respond to brighter light and make possible detailed color vision. Some cones are most sensitive to red light, others to green and others to blue. Their combined response enables you to see all the colors in this magazine. When all three types of cones are excited equally, the color you see is pure white.

Most animals are limited in their ability to see in color, and many do not see color at all. “Colour vision adds immensely to the joys of life,” says surgeon Rendle Short, adding: “Of all the organs of the body not absolutely essential for life, the eye may be considered the most wonderful.”

“Miraculous Teamwork”

Images fall upside down on the retina just as they do on a camera’s film. “Why is the world not upside down to us?” asks Dr. Short. “Because,” he explains, “the brain has developed the habit of reversing the impressions.”

Special glasses have been designed to turn the image around. In scientific experiments, people who wore such glasses saw everything upside down. Then, after a few days, something amazing happened. They began to see normally! “The miraculous teamwork of your eye and your brain is exhibited in a number of ways,” comments The Body Book.

As your eye moves across this line, the cones distinguish the black ink from the white paper. Your retina, however, cannot respond to characters of a man-made alphabet. We learn to give meaning to a string of characters in another part of the brain. A transfer of information is needed.

The retina sends a coded message via a million nerve fibers to a part of your brain situated near the back of your head. “The projections from the retina to the cerebral cortex,” explains the book The Brain, “are highly organized and orderly. . . . If a small light is shined on each different part of the retina, a corresponding part of the visual area [in the brain] will respond.”

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Unlike a camera, because the retina has such a wide range of sensitivity to light, the eye is not dependent on flash equipment

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Your retina has millions of neurons, called cones, which are sensitive to green, red, or blue

The Brain​—“More Than a Computer”

ANOTHER superb organ is the human brain. It, together with the rest of the nervous system, is often compared to man-made computers. Of course, computers are constructed by humans and operate according to step-by-step instructions predetermined by human programmers. Yet, many people believe that no intelligence was responsible for “wiring” and “programming” the human brain.

Although extremely fast, computers handle only one piece of information at a time, whereas the human nervous system processes millions of pieces of information simultaneously. For example, during a stroll in the springtime, you can enjoy the beautiful scenery, listen to the song of birds, and smell the flowers. All these pleasant sensations are transmitted simultaneously to your brain. At the same time, streams of information flow from the sense receptors in your limbs, informing your brain of the moment-to-moment position of each leg and the state of each muscle. Obstacles in the footpath ahead are noticed by your eyes. On the basis of all this information, your brain ensures that each step is taken smoothly.

Meanwhile, the lower regions of your brain govern your heartbeat, breathing, and other vital functions. But your brain handles much more. As you walk, you can sing, talk, compare present scenes with past scenes, or make plans for the future.

“The brain,” concludes The Body Book, “is much more than a computer. No computer can decide that it is bored or wasting its talents and should embark on a new way of life. The computer cannot drastically alter its own program; before it sets out in a new direction, a person with a brain must reprogram it. . . . A computer cannot relax, or daydream, or laugh. It cannot become inspired or creative. It cannot experience consciousness or perceive meaning. It cannot fall in love.”

The Most Wonderful Brain of All

Animals such as elephants and some large sea creatures have brains larger than that of a human, but in proportion to body size, the human brain is the largest of all. “The gorilla,” explains Richard Thompson in his book The Brain, “is physically larger than a human yet has a brain only one-fourth the size of the human one.”

The number of different pathways between neurons (nerve cells) in the human brain is astronomical. This is because neurons have so many interconnections; one neuron may connect up with over one hundred thousand others. “The figure of possible connections within our modern brain is as good as infinite,” states Anthony Smith in his book The Mind. It is larger “than the total number of atomic particles that make up the known universe,” says neuroscientist Thompson.

But there is something even more remarkable. It is the way this vast network of neurons has been connected that enables humans to think, speak, listen, read, and write. And these things can be done in two or more languages. “Language is the crucial difference between humans and animals,” states Karl Sabbagh in his book The Living Body. Animal communication is simple by comparison. The difference, admits evolutionist Sabbagh, “is not just a trivial improvement on other animals’ abilities to make noises​—it is the fundamental property that makes humans human, and it is reflected in major differences in brain structure.”

The marvelous structure of the human brain has motivated many to make better use of its potential by becoming skilled at some trade, learning to play a musical instrument, mastering another language, or developing whatever talents add joy to life. “When you learn a new skill,” write Drs. R. and B. Bruun in their book The Human Body, “you are training your neurons to connect in a new way. . . . The more you use your brain, the more efficient it will become.”

Made by Whom?

Could something so highly organized and orderly like the hand, the eye, and the brain have come about by chance? If man is credited with inventing tools, computers, and photographic film, surely someone should be honored for making the more versatile hand, eye, and brain. “O Jehovah,” the Bible psalmist said, “I shall laud you because in a fear-inspiring way I am wonderfully made. Your works are wonderful, as my soul is very well aware.”​—Psalm 139:1, 14.

Many wonderful functions of the human body take place without our conscious effort. Future issues of this magazine will discuss some of these amazing mechanisms, and also whether aging, sickness, and death can be conquered, so that we can enjoy life forever!

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Your Wonderful Neurons

A NEURON is a nerve cell with all its processes. Your nervous system contains many types of neurons, which total about 500 billion. Some are sense receptors that send information from different parts of the body to your brain. Neurons in the higher region of your brain function like a video recorder. They can permanently store information that comes from your eyes and ears. Years later you can “play back” these sights and sounds, along with thoughts and other sensations that no man-made machine can record.

Human memory is still a mystery. It has something to do with the way neurons connect. “The average brain cell,” explains Karl Sabbagh in his book The Living Body, “links up with about 60,000 others; indeed some cells have links with up to a quarter of a million others. . . . The human brain could hold at least 1000 times as much information in the pathways connecting its nerve cells as is contained in the largest encyclopedia​—say 20 or 30 big volumes.”

But how does one neuron pass information to another? Creatures with a simple nervous system have many nerve cells that are joined together. In such a case, an electrical impulse crosses the bridge from one neuron to the next. The crossing is called an electrical synapse. It is fast and simple.

Strange as it may seem, most neurons in the human body pass messages via a chemical synapse. This slower, more complex method can be illustrated by a train that reaches a river without a bridge and has to be ferried across. When an electrical impulse reaches a chemical synapse, it has to stop because a gap separates the two neurons. Here the signal is “ferried” across by the transfer of chemicals. Why this complex electro-chemical method of passing nerve impulses?

Scientists see many advantages in the chemical synapse. It ensures that messages pass one way. Also, it is described as plastic because its function or structure can easily change. Here signals can be modified. Through use, some chemical synapses get stronger while others disappear because of disuse. “Learning and memory could not develop in a nervous system that had only electrical synapses,” states Richard Thompson in his book The Brain.

Science writer Smith explains in his book The Mind: “Neurons do not just fire and not fire . . . they must be capable of passing on much more subtle information than yes or no. They are not just hammers hitting the next nail, either more frequently or less so. They are, to complete this analogy, a carpenter’s kit, with screwdrivers, pliers, pincers, mallets​—and hammers. . . . Each neural impulse is transformed along the way, and nowhere else than at the synapses.”

The chemical synapse has a further advantage. It takes less space than an electrical synapse, which explains why the human brain has so many synapses. The journal Science gives a figure of 100,000,000,000,000​—equivalent to the number of stars in hundreds of Milky Way galaxies. “We are what we are,” adds neuroscientist Thompson, “because our brains are basically chemical machines rather than electrical ones.”

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Why Your Brain Needs So Much Blood

BEFORE diving into a swimming pool, perhaps you dip your toes into the water. If the water is cold, tiny cold receptors in your skin quickly respond. In less than a second, your brain registers the temperature. Pain receptors can transmit information even more quickly. Some nerve impulses reach speeds of 225 miles [360 km] per hour​—comparable to running the length of a football field in one second.

How, though, does the brain work out the intensity of a sensation? One way is by the frequency with which a neuron fires; some fire a thousand or more times a second. The intense activity that takes place among neurons in the brain would be impossible were it not for the work of pumps and powerhouses.

Each time a neuron fires, atoms with an electrical charge pour into the cell. If these sodium ions, as they are called, are allowed to accumulate, the neuron will gradually lose its ability to fire. How is the problem solved? “Every neuron,” explains science writer Anthony Smith in his book The Mind, “contains about a million pumps​—each one is a slight bump on the cell membrane—​and every pump can swap about 200 sodium ions for 130 potassium ions every second.” Even when neurons rest, the pumps keep working. Why? To counteract the effect of sodium ions that leak into the cell and potassium ions that leak out.

The activity of the pumps requires a constant supply of energy. The energy comes from tiny mitochondria, or “powerhouses,” scattered inside each cell. To produce energy, each powerhouse needs oxygen and glucose supplied by the blood. No wonder your brain needs so much blood. “Although it constitutes only about 2 percent of total body weight,” explains Richard Thompson in his book The Brain, it “receives 16 percent of the blood supply . . . Brain tissue receives 10 times as much blood as muscle tissue.”

The next time you feel the temperature of water, be thankful for the trillions of pumps and powerhouses in your brain. And remember that all this activity is possible because of oxygen and glucose transported by your blood.

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The human brain processes millions of bits of information simultaneously. As you move, sense receptors in your limbs inform your brain of the moment-to-moment position of each arm and the state of each muscle

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The brain is far more complex and versatile than a computer