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1、12月英语四六级考试阅读提高练习(21)The Story of Progress and DiscoveryYou have probably heard it said that if you put a horsehair in a container of rainwater and place it in the sunshine, a snake will develop. It is hard to convince people even today that this is not true, yet it is not difficult to get a horsehai
2、r and some rainwater to try the experiment. Since very early times men have believed that living things could come from non-living things. Some people thought that frogs and toads developed from the mud of ponds, rats from the river Nile, and insects from dew or from rotting waste. Vergil wrote that
3、 slime begat(产生) frogs. Centuries later, other men wrote that water produced fishes and that mice came from old rags. This notion that living things can come from lifeless matter is known as the theory of spontaneous generation. Today we know that living things can come only from living things. Redi
4、, in the seventeenth century, was the first to experiment to prove that insects do not originate from rotting matter. From his experiment, Redi concluded that maggots appear in decaying meat simply because the eggs of flies hatch there, and not from spontaneous generation.At the time of Leeuwenhoek
5、the microscope was not well developed, but with it he discovered bacteria. The study of these tiny forms of life which looked like specks(小污点) to him was not practical until more than 150 years later, when microscopes were much improved. However, the discovery led some medical men at the time to thi
6、nk that contagious diseases were due to germs passed from the sick to the well.Dr. Edward Jenner, a young English physician, overheard a milkmaid say that she was not afraid of smallpox because she had just recovered from an attack of cowpox. This gave Jenner the clue, and in 1796 he proved that a p
7、erson vaccinated with cowpox germs is quite certain to escape from getting smallpox. At this time smallpox was so common that about only one person in a hundred escaped.In Aristotles days, it was the common belief that air caused foods to spoil. People believed that this was true until the seventeen
8、th century. In 1800, Napoleon offered a prize for the successful invention of a container which would keep foods from spoiling in war times. The prize was won by Francois Appert, who had worked all his life on this problem. He packed foods in glass or china jars, poured in enough water to cover the
9、food, corked and sealed them, then placed the jars in a container of water which was gradually heated to the boiling point. He thought, however, that it was air that caused the foods to spoil. It was not until fifty years later that Louis Pasteur proved that it was not air that spoiled foods, but ti
10、ny living organisms that float about in the air. The first tin-can container was made in 1807 by Peter Durand. The canning industry in the United States began in 1819 when salmon, lobster, and oysters were first canned.The idea that germs cause disease did not have many followers when it was first s
11、uggested. Interest began to be shown again when Bassi, in 1837, showed that a silkworm disease was transmitted to healthy worms by the passing of tiny glittering particles. Later, Henle said that catching diseases were caused by germs.About 1850, Louis Pasteur began experimenting with tiny living or
12、ganisms and was able to discover many important things. He proved that yeast plants cause substances to ferment, that bacteria cause milk to sour, and that floating particles in the air contain living germs which cause spoiling and decay.Soon after Pasteur had announced these discoveries, Joseph Lis
13、ter proved that wounds were poisoned by germs from the air or from the surgeons instruments used during operations. He proved that if the instruments were perfectly clean or sterile and if antiseptic (防腐剂) dressings were used on wounds to prevent the entrance of germs, wounds would heal without deca
14、y or blood poisoning. The first antiseptic Lister used was carbolic acid(石炭酸). The wards in the Glasgow infirmary of which Lister had charge were especially affected by gangrene (坏蛆). In a short time they became the healthiest of any known, because he applied his knowledge of antiseptics to the heal
15、ing of wounds. With some improvements, Listers methods are used today.Major Laveran was the first to discover that a certain germ was always present in the blood of patients who had malaria. Eight years later, in 1888, Major Ross proved that he found a similar germ in the body of the Anopheles mosqu
16、ito. Then, by other experiments, it was shown that the germs that cause malaria can be transmitted only by the bite of the mosquito. To prove this, two physicians in London permitted themselves to be bitten by mosquitoes which had previously bitten malarial patients in Italy and ten were shipped in a box to London. In eighteen days after being bitten by these mosquitoes, both physicians developed malarial fever. Soon it was proved that the germs of yellow fever we
