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The modern age is an age of electricity. People are so used to electriclights, radio, televisions, and telephones that it is hard to imagine whatlife would be like without them. When there is a power failure, people gropeabout in flickering candlelight, cars hesitate in the streets becausethere are no traffic lights to guide them, and food spoils in silent refrigerators. Yet, peoplebegan to understand how electricity works only a little more than two centuriesago. Nature has apparently been experimenting in this field for millionsof years. Scientists are discovering more and more that the living worldmay hold many interesting secrets of electricity that could benefit humanity. All livingcells send out tiny pulses of electricity. As the heart beats, it sends outpulses of record; they form an electrocardiogram, which adoctor can study to determine how well the heart is working. Thebrain, too, sends out brain waves of electricity, which can be recorded inan electroencephalogram. The electric currents generated bymost living cells are extremely small -- often so small that sensitiveinstruments are needed to record them. But in some animals, certain musclecells have become so specialized as electrical generators that they do not workas muscle cells at all. When large numbers of these cells are linked together, the effects can beastonishing. The electriceel is an amazing storage battery. It can send a jolt of as much as eighthundred volts of electricity through the water in which it lives. As many as four-fifths of all the cells in the electric eels body are specialized for generatingelectricity, and the strength of the shock it can delivercorresponds roughly to the length of its body. | 
