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提问人:网友sycb01 发布时间:2022-01-06

Regeneration of Limbs Most people would agree that it would be wonderful if humans could r

Regeneration of Limbs

Most people would agree that it would be wonderful if humans could regenerate limbs. These who have lost their arms or legs would be complete again. The day is still far off when this might happen. But in the last 10 years, doctors have reported regeneration in smaller parts of the body, most often fingers.

Regeneration is not a newly-discovered process. For centuries, scientists have seen it work in some kinds of animals. Break off a lizard's (蜥蜴的) tail, for example, and it will grow a new tail. Scientists now are looking for a way to turn on this exciting ability in more highly-developed animals, including humans. Their experiments show that nerves, cell chemistry and the natural electric currents in the body all seem to have a part in this process.

The body of every animal contains general purpose cells that change into whatever kind of cells the body needs. Animals such as the lizard or salamander (蝾螈) use these cells to regenerate a new tail or leg when the old one is broken off. These cells collect around the wound. They form. a mass called a blastama (胚基). The cells of the blastema begin to change. Some become bone cells, some muscle cells, some skin cells. Slowly, a new part regrows from the body outward. When completed, the new part is just like the old one.

Mote than 200 years ago, Italian scientist Luigi Spallanzani showed that younger animals have a greater ability to regenerate lost parts than older animals. So do animals lower on the ladder of evolutionary development. The major difference seems to be that less-developed animals have more nerves in their tails and legs than humans do in their arms and legs.

Another helpful piece of information was discovered in the late 1600s. Scientists found that when a creature is injured, an electrical current flows around the wound. The strength of the current depends on how severe the wound is and on how much nerve tissue is present.

In 1945, American scientist Meryl Rose tested another idea about regeneration. He thought a new limb might grow only from an open wound. Doctor Rose cut off the front legs of some frogs, below the knee. He kept the wounds wet with a strong salty liquid. This prevented skin from growing over the wounds. The results were surprising. Frogs do not regenerate new legs naturally. But these frogs began to grow new limbs. About half of each cut-off leg grew back again. New bones and muscles developed.

This research has led doctors to new ways of treating cut-off fingers. Doctors have observed, for example, that many children and some adults will regrow the top of a finger if the wound is left open.

The passage indicates that

A.humans can never regenerate limbs.

B.humans might be able to regenerate limbs in the future.

C.human limbs may be regenerated on some animals first.

D.regeneration of human limbs will soon become a reality.

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完形填空。????It was the afternoon of December 24, ...

    It was the afternoon of December 24, the day before Christmas;and as the newest doctor in our

office, I had to work. The only thing that   1  my day was the beautifully decorated Christmas tree in

our waiting room and a   2  sent to me by a fellow I was dating - a dozen long-stemmed red roses.

    Then I was told a lady  3  needed to speak with me. As I stepped out, I noticed a young,

tired-looking woman with a   4  in her arms. Nervously, she   5  that her husband - a prisoner in a

nearby prison-was my   6  patient. She told me she wasn't   7  to visit her husband in prison and

that he had never seen his   8  . Her request was for me to let the boy's father sit in the waiting room

with her as   9  as possible before I called him for his appointment. I agreed.   10  , it was Christmas


    Her husband arrived-with chains on his feet and hands, and two armed guards. The woman's tired

face   11  like our Christmas   12  when her husband took a seat beside her. After almost an hour, I

called the   13  to my office.

    At the end of the   14  , I wished him a Merry Christmas - a(n)   15  thing to say to a man headed

back to prison. He   16  and thanked me. He also said he felt   17  by the fact he hadn't been able to

get his wife anything for Christmas. On   18  this, I was inspired with a wonderful idea.

    I'll never forget the look on both their faces as the prisoner gave his wife the beautiful   19  . I'm not

sure who experienced the most joy - the husband in giving, the wife in   20  , or myself in having the

opportunity to share in this special moment.

(    ) 1. A. darkened

(    ) 2. A. report  

(    ) 3. A. urgently

(    ) 4. A. dog      

(    ) 5. A. explained

(    ) 6. A. first    

(    ) 7. A. shown    

(    ) 8. A. wife    

(    ) 9. A. soon    

(    )10. A. After all

(    )11. A. went red

(    )12. A. day      

(    )13. A. prisoner

(    )14. A. preparation

(    )15. A. rude    

(    )16. A. cried    

(    )17. A. amused  

(    )18. A. hearing  

(    )19. A. clothes  

(    )20. A. winning  

B. brightened

B. patient  

B. strangely

B. box      

B. learned  

B. last      

B. allowed  

B. doctor    

B. close    

B. Above all

B. lit up    

B. cake      

B. woman    

B. celebration

B. difficult

B. shouted  

B. frightened

B. seeing    

B. roses    

B. meeting  

C. shortened  

C. gift      

C. regularly  

C. quilt      

C. realized  

C. best      

C. persuaded  

C. son        

C. long      

C. In addition

C. clouded over

C. party      

C. guard      

C. appointment

C. proper    

C. disagreed  

C. saddened  

C. realizing

C. pictures  

C. borrowing 

D. worsened      

D. message        

D. unreasonably  

D. baby          

D. insisted      

D. next          

D. forbidden      

D. victim        

D. quietly        

D. Sure enough    

D. turned aside  

D. tree          

D. others        

D. punishment    

D. easy          

D. smiled        

D. encouraged    

D. considering    

D. decorations    

D. receiving      

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For centuries, in the countries of south and Southeast Asia the elephant has been an intimate part of the culture, economy and religion, and nowhere more so than in Thailand. Unlike its African cousin, the Asian elephant is easily domesticated (驯化). The rare so-called white elephants have actually lent the authority of kingship to its rulers and until the 1920s the national flag was a white elephant on a red background.To the early Western visitors the country’s romantic name was “Land of the White Elephant”.
Today, however, the story is very different. Out of work and out of land, the Thai elephant struggles for survival in a nation that no longer needs it. The elephant has found itself more or less abandoned by previous owners who have moved on to a different economic world and a westernized society. And while the elephant’s problems began many years ago, now it rates a very low national priority.
How this reversal from national icon (圣像) to neglected animal came about is a tale of worsening environmental and the changing lives of the Thais themselves. According to Richard Lair, Thailand’s experts on the Asian elephant and author of the report Gone Astray, at the turn of the century there may well have beenas many as 100,000 domestic elephants in the country. In the north of Thailand alone it was estimated that more than 20,000 elephants were employed in transport, 1,000 of them alone on the road between the cities of Chiang Mai and Chiang Saen. This was at a time when 90 per cent of Thailand was still forest—a habitat (栖息地) that not only supported the animals but also made them necessary to carry goods and people. Nothing ploughs through dense forest better than a massive but sure-footed elephant.
By 1950 the elephant population had dropped to a still substantial 13,397, but today there are probably nomore than 3,800, with another 1,350 roaming free in the national parks. But now, Thailand’s forest coversonly 20 per cent of the land. This deforestation (采伐森林) is the central point of the elephant’s difficult situation, for it has effectively put the animals out of work. This century, as the road network grew, so the elephant’s role as a beast of burden declined.
Choose correct answers to the question: What can we know about African elephants from the passage?
A.It is easy to tame them.
B.It is hard to tame them.
C.They are living a better life than Asian elephants.
D.Their fate is quite similar to that of Asian elephants.
Thailand was once called “Land of the White Elephant” because_______.A.white elephant is rarely seen and thus very special
B.white elephant was a national symbol until the 1920s
C.white elephant has helped kings to gain the ruling authority
D.this name was so romantic that it was popular among visitors
Why is the Thai elephant “out of work”, according to the author?A.Because the elephants are no longer useful to their owners.
B.Because their owners are westernized and neglect them.
C.Because the government pays little attention to the problem.
D.Because there are too many elephants and too few jobs.
Which of the following statements is true about the elephant population at various times?A.There were 100,000 tamed elephants at the turn of the century.
B.20,000 elephants were employed in transport in Thailand at the turn of the century.
C.By 1950 the elephant population in Thailand has been quite small.
D.Today the elephant population is estimated at 5,150.
The passage is most probably from_______.A.a travel magazine
B.a history book
C.a research report
D.an official announcement

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The greatest influence on Middle English vocabulary is from Latin.



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