2009年11月27日星期五
Electricity
The modern yard Inflatable Arches 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 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 electrichouse Christmas Inflatable 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.
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.