Electricity
The modern age is an age of electricity. People are so used to electric lights, radio, televisions, and telephones that it is hard to imagine what life would be like without them. When there is a power failure, people grope about in flickering candlelight, cars hesitate in the streets because there are no traffic lights to guide them, and food spoils in silent refrigerators.
Yet, people began to understand how electricity works only a little more than two centuries ago. Nature has apparently been experimenting in this field for million of years. Scientists are discovering more and more that the living world may hold many interesting secrets of electricity that could benefit humanity.
All living cell send out tiny pulses of electricity. As the heart beats, it sends out pulses of record; they form an electrocardiogram, which a doctor can study to determine how well the heart is working. The brain, too, sends out brain waves of electricity, which can be recorded in an electroencephalogram. The electric currents generated by most living cells are extremely small - often so small that sensitive instruments are needed to record them. But in some animals, certain muscle cells have become so specialized as electrical generators that they do not work as muscle cells at all. When large numbers of these cell are linked together, the effects can be astonishing.
The electric eel is an amazing storage battery. It can seed a jolt of as much as eight hundred volts of electricity through the water in which it live. ( An electric house current is only one hundred twenty volts.) As many as four-fifths of all the cells in the electric eel’s body are specialized for generating electricity, and the strength of the shock it can deliver corresponds roughly to length of its body.
电
现代是一个电力时代。人们对电灯、收音机、电视和电话如此习惯，以至于很难想象没有它们生活会是什么样子。当停电时，人们在摇曳的烛光中摸索着，汽车在街道上犹豫，因为没有红绿灯来引导他们，而无声冰箱里的食物会变质。
然而，人们仅仅在两个多世纪以前就开始了解电的使用原理了。显然，大自然已经在这个领域进行了数百万年的试验。科学家们越来越多地发现，生活世界可能包含许多有益于人类的电能的有趣秘密。
所有活细胞都发出微小的电脉冲。当心脏跳动时，它发出记录的脉冲，形成心电图，医生可以研究心脏的运作情况。大脑也发出电能的脑电波，可以在脑电图中记录下来。大多数活细胞所产生的电流非常小——通常很小，需要灵敏的仪器来记录它们。但是在某些动物身上，某些肌肉细胞变得像发电机那样专业，以至于它们根本就不起肌肉细胞的作用。当大量的这些细胞连接在一起时，效果会令人吃惊。
电鳗是一种神奇的蓄电池。它可以通过它所生活的水产生多达八百伏的电力。（电流只有一百二十伏特），电鳗体内的所有细胞中有五分之四是专门用来发电的，而且电击所产生的震动强度与身体的长度大致相当。
