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