”I am Your Body”

HAND

     YOU THINK LOSING eyes or legs would be supreme disasters. Losing my partner and me would be a far greater one. I am your left hand. I can't perform chemical miracles like your liver, or electrochemical wonders like your brain. Basically, I am a piece of machinery, a bewildering array of levers, hinges and power sources, all managed by a master computer - your brain. In complexity I dwarf man-made machines. I am versatile, tireless, and swift. If you are an exceptional typist, my partner and I could put 120 or more words on paper each minute.

A measure of the importance of any body part is the size of the brain area reserved for its use. We hands have two of the largest spaces in the area of the brain known as the motor cortex. When you rotate your thumb, you are witnessing an amazing event. Thousands of messages from the brain are required for this simple act, ordering this muscle to contract, that one to relax; causing this tendon to pull, that one to rest.

From birth to death we hands are almost never still - except for some rest during sleep. During your lifetime I will extend and flex finger joints at least 25 millions times. Legs, arms, shoulders, feet and other parts of your body tire with sustained activity. But how often do you complain about tired hands.

Even when you as a baby emerged from the womb we hands were quite well developed. We were strong enough to support your body weight - and before long we would hang from the obstetrician's thumbs. Considering the remoteness of many of the muscles that control me - in your forearm - my strength is surprising. You can exert a grip of 90 pounds; if you are super-strong it might go up to 120 or higher. (Women generally have only about half as much grip as a man.)

If you are right handed then you are the same as approximately 95 percent of the people. You began to choose handedness when you were about six months old. At the same time you began to coordinate hand and eye movements - learning to look at something and pick it up. This period was a landmark in your development.

Until man's forebears assumed upright postures they were among the most defenseless of creatures: a snack for a lion or a tiger, easy prey for a hyena. But once erect posture freed us hands from the job of locomotion, we could fashion and use weapons and tools. Then the naked ape achieved mastery over earth and its creatures. Then, too, the jaws, freed of foraging and fighting responsibilities, shrank in size and could begin to experiment with language. As our tasks became more complex, the brain began to grow. You, the end product of all this, can give us much of the credit for starting you up the evolutionary ladder.

The strange thing is that meanwhile - not a great deal was happening to us - we aren't much different structurally from hands of other primates. But we are infinitely more skilled.

We can even substitute for eyes, ears, voice. If you were blind, you could use us to read Braille. If deaf, you could "speak" with us by using sign language. Our tactile discrimination is so keen that you don't have to look at the coins in your pocket to find a quarter. My fingers can pick one out for you. If you were a farmer, you could run soil through your hands and determine its texture; if a housewife, she could judge by feel the quality of a fabric. These are extraordinary achievements.

We hands can take a certain amount of credit for some important intellectual achievements, too. We played a part in the development of mathematics - the decimal system is based on the ten digits my partner and I possess, as well as your ten toes.

Structurally, we are the most intricate components of your body. In no other part of the body is so much machinery packed into so small a space. I have 8 wrist bones, 5 bones in my palm, 14 in my digits - a total of 27. Add my partner's 27 and we account for more than a fourth of the bones in your body. My supply of nerves to detect heat, touch and pain is one of the most elaborate in the body. I have thousands of nerve endings per square inch, most heavily concentrated in my fingertips. Sensitivity here is extraordinary. you can feel your way in the dark, moisten a fingertip and determine direction of the wind and do a thousand other things that you considers common place - instead of looking on them as the true wonders they are.

My tendons are the power trains, the connecting linkup between my many jointed bones and the remote muscles which move them. (You can feel tendons in your forearm move when you flex a finger.) For binding material I have a maze of ligaments, plus fascia, which is a layer of connective tissue providing foundation material for nerves, blood vessels and other components. I don't have room for a big network of arteries and veins, but I do have a rich network of capillaries. I suffer on a cold day while the rest of your body is quite comfortable because the peripheral nature of my digits - they are far from your heart - allows your blood to cool.

My digits are, of course, my main working parts. The real virtuoso is my thumb; it is "opposed" to the other four, can swing to touch all of them and provide grip. It does about 45 percent of my useful work - just try to write without it, lift a glass of water or shake hands. You could get along quite well without any one of my other four digits, or even if only stubs of them remained. But take away my thumb and I would be like a pair of pliers with one jaw missing. My digits become less independent as they move away from the thumb, and the little fifth one is the least independent of all.

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