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.

　　5、The Beginning of Drama

　　There are many theories about the beginning of drama in ancient Greece. The on most widely accepted today is based on the assumption that drama evolved from ritual. The argument for this view goes as follows. In the beginning, human beings viewed the natural forces of the world-even the seasonal changes-as unpredictable, and they sought through various means to control these unknown and feared powers. Those measures which appeared to bring the desired results were then retained and repeated until they hardened into fixed rituals. Eventually stories arose which explained or veiled the mysteries of the rites. As time passed some rituals were abandoned, but the stories, later called myths, persisted and provided material for art and drama.

　　Those who believe that drama evolved out of ritual also argue that those rites contained the seed of theater because music, dance, masks, and costumes were almost always used, Furthermore, a suitable site had to be provided for performances and when the entire community did not participate, a clear division was usually made between the "acting area" and the "auditorium." In addition, there were performers, and, since considerable importance was attached to avoiding mistakes in the enactment of rites, religious leaders usually assumed that task. Wearing masks and costumes, they often impersonated other people, animals, or supernatural beings, and mimed the desired effect-success in hunt or battle, the coming rain, the revival of the Sun-as an actor might. Eventually such dramatic representations were separated from religious activities.英语作文
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