2014考研英語：閱讀理解基礎(chǔ)階段練習(xí)題(八)_跨考網(wǎng)

　　2014考研英語：閱讀理解基礎(chǔ)階段練習(xí)題(八)

　　Text 8

　　In the early days of sea travel, seamen on long voyages lived exclusively on salted meat and biscuits. Many of them died of scurvy, a disease of the blood which causes swollen gums, livid white spots on the flesh and general exhaustion. On one occasion, in 1535, an English ship arrived in Newfound-land with its crew desperately ill. The men’s lives were saved by Iroquois Indians who gave them vegetable leaves to eat. Gradually it came to be realized that scurvy was caused by some lack in the sailors’ diet and Captain Cook, on his long voyages of discovery to Australia and New Zealand, established the fact that scurvy could be warded off by the provision of fresh fruit for the sailors.

　　Nowadays it is understood that a diet which contains nothing harmful may yet result in serious disease if certain important elements are missing. These elements are called “vitamins”. Quite a number of such substances are known and they are given letters to identify them, A,B,C,D, and so on. Different diseases are associated with deficiencies of particular vitamins. Even a slight lack of Vitamin C, for example, the vitamin most plentiful in fresh fruit and vegetable, is thought to increase significantly our susceptibility to colds and influenza.

　　The vitamins necessary for a healthy body are normally supplied by a good mixed diet, including a variety of fruit and green vegetables. It is only when people try to live on a very restricted diet, say during extended periods of religious fasting, or when trying to lose weight, that it is necessary to make special provision to supply the missing vitamins.

　　Another example of the dangers of a restricted diet may suffer from ‘beriberi’, which used to afflict large numbers of Eastern peoples who lived mainly on rice. In the early years of this century, a Dutch scientist called Eijkman was trying to discover the cause of beriberi. At first he thought it was transmitted by a germ. He was working in a Japanese hospital, where the patients were fed on rice which had had the outer husk removed from the grain. It was thought this would be easier for weak, sick people to digest.

　　Eijkman thought his germ theory was confirmed when he noticed the chickens in the hospital yard, which were fed on scraps from the patients’ plates, were also showing signs of the disease. He then tried to isolate the germ he thought was causing the disease, but his experiments were interrupted by a hospital official, who decreed that the huskless polished rice, even though left over by the patients, was too good for chickens. It should be recooked and the chickens fed on cheap, coarse rice with the outer covering still on the grain.

　　Eijkman noticed that the chickens began to recover on the new diet. He began to consider the possibility that a lack of some ingredient in the husk might be the cause of the disease. Indeed this was the case. The element needed to prevent beriberi was shortly afterwards isolated from rice husks and is now known as vitamin B. The milled rice, though more expansive, was in fact perpetuating the disease the hospital was trying to cure. Nowadays, this terrible disease is much less common thanks to our knowledge of vitamins. (553 words)