Many processes in the body naturally turn on or off with a near-clocklike precision. Sleeping and changes in body temperature， mood and metabol-ism - the process of turning food into energy - all follow a cycle. The body clock can get out of whack when a person travels to a distant place in a different time zone or works the night shift. Such disruptions may cause extreme tiredness.

Cells of the immune system usually help fight off infections and toxic invaders， but if they get too many together at one time， they could get rowdy. They can cause problems. And that's the case with TH17 cells. These cells normally kill germs by causing inflammation. Its a common body response to injuries. But too much inflammation can backfire. It could even underlie a variety of diseases， including asthma， allergies.

A research team reset the body clocks of mice by six hours. They did this by changing when the animals woke up and were exposed to light. The experiment mimicked the jet lag travelers experience when they journey far enough that their waking and sleeping times no longer match what their body clock was used to. Changes occurred in the gut of mice experiencing lab version of jet lag. Lots of TH17 cells accumu-lated. The scientists didn't find a similar hoard of immune cells in the guts of mice whose body clocks continued to keep normal time.

The scientists also exposed mice to chemicals that can trigger immune problems. These chemicals were more likely to trigger inflammation in jet-lagged mice than in mice whose body clocks were operating normally. That suggests that resetting the internal clock may make an animal more likely to develop immune disorders.

人體內(nèi)的許多生物過程都以近似時(shí)鐘的精確度自然地打開或關(guān)閉。睡眠、體溫變化、情緒以及將食物轉(zhuǎn)變?yōu)槟芰康男玛惔x等，都是按照一定周期運(yùn)行的。當(dāng)人們進(jìn)行長距離旅行，到達(dá)不同時(shí)區(qū)或者上晚班時(shí)，生物鐘就可能被打亂，從而導(dǎo)致極度疲倦。

免疫細(xì)胞通常能幫助抵抗感染和有毒入侵者，但是如果它們過多地聚集在一起，就會變得雜亂無章、引起麻煩。TH17型細(xì)胞即如此。免疫細(xì)胞用激發(fā)炎癥的方式來殺滅細(xì)菌，這是人體對傷害的正常反應(yīng)。但是炎癥過于嚴(yán)重會起反作用，甚至可能引起哮喘、過敏、心臟病等疾病。

研究團(tuán)隊(duì)通過改變蘇醒時(shí)間以及與燈光接觸時(shí)間，對老鼠的生物鐘進(jìn)行了時(shí)差6個(gè)小時(shí)的重置。該實(shí)驗(yàn)?zāi)７铝寺眯姓叩娘w行時(shí)差體驗(yàn)。實(shí)驗(yàn)室中的老鼠在體驗(yàn)了實(shí)驗(yàn)環(huán)境中的飛行時(shí)差后體內(nèi)發(fā)生了改變，大量免疫細(xì)胞堆積，而生物鐘沒有被擾亂的老鼠體內(nèi)卻沒有類似的免疫細(xì)胞聚集現(xiàn)象。

另外，科學(xué)家們還讓老鼠接觸了會引起免疫問題的化學(xué)物質(zhì)，結(jié)果發(fā)現(xiàn)相對于生物鐘正常運(yùn)轉(zhuǎn)的老鼠而言，這些化學(xué)物質(zhì)在有時(shí)差反應(yīng)的老鼠身上引起炎癥的可能性更大，這表明：重置生物鐘容易使動物患上免疫性疾病。

（注意斜體字的譯法）

One warm summer day， I heard the familiar tune of an ice cream truck outside my window. That night as I was going to bed I heard it again， faintly in the distance. But why was an ice cream truck cruising the neighborhood so late， at nearly （1） m ？ It wasn't. Gradually I realized the tune was not coming from outside my window. It had been playing inside my head.

It's true that some types of hallucinations（幻覺）are associated with mental （A） i . But many healthy people also experience "phantom" （幽靈）senses. Some hear music that isn't there. Some see visions. Others live with imaginary smells filling up their noses.

Hallucination is a unique and special （B） c of consciousness and mental life. Though hallucinations are probably as old as the human brain， our understanding of them has greatly increased over the last few （C） d . That's happening because of new technology that lets experts peer inside the （2） b . There is still a lot to discover about these ghosts in our heads.

Sometimes people hear a （3） m . Is the melody that you hear real， or is it all in your head？ Some people have a hard time telling. In one case， a woman woke to the sound of loud music. She asked her apartment manager to tell her （D） n to turn down their radio. In fact， there had been no music. But the woman didn't believe it， so she called the police to make a complaint about the noise！

Some researchers have looked at the brains of people who hear phantom tunes. Tim Griffiths is a UK neurologist. He used a （E） t called PET（Positron Emission Tomography， 正電子成像術(shù)）to view the brains of six people. All had hearing loss and heard phantom music. The PET scans showed blood flow in the brain， revealing which brain （F） r were most active. When his patients "heard" phantom music， a network of brain regions became very active. This （4） a

was similar to what neurologists see in the brains of normal people listening to real music.

（A， B， C， D， E， F FOR CROSS， 1， 2， 3， 4 FOR DOWN. The first letters of the absents were given）

They call me a man， but I'll never have a wife.

I was given a body， but not given life.

They made me a mouth， but didn't give me breath.

Water gives me life and sun brings me death.

What am I？