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Primer on Smell In addition to bring

tikufree2019-12-17  13
问题 Primer on Smell   In addition to bringing out1 the flavor of food, what does the sense of smell do for us ?   Smell “gives us information about place, about where we are,” says Randall Reed, a Johns Hopkins University professor whose specialty is the sense of smell. ___1___ “Whether we realize it or not, we collect a lot of information about who is around us based on smell,” says Reed.   Even at a distance, odors can warn us of2 trouble — spoiled food, leaking gas, or fire. “It’s a great alert,” offers Donald Leopold, a doctor at Johns Hopkins. For example, if something in the oven is burning, everyone in the house knows it.   With just a simple scent, smell can also evoke very intense emotion. Let’s say, for example, that the smell is purple petunias. ___2___ Now let’s imagine that your mother died when you were three, and she used to have a flower garden. You wouldn’t need to identify the smell or to have conscious memories of your mother or her garden. You would feel sad as soon as you smelled that spicy odor.   Compared with3 animals, how well do people detect smelts ?   That depends on what you mean by “how well”. We are low on receptor cells ： current estimates say that humans have roughly five million smell-receptor cells, about as many as a mouse. ___3___   Reed says that, across species, there is a relatively good correlation between the number of receptor cells and how strong the sense of smell is. “You can hardly find the olfactory bulb in a human brain —— it’s a pea-sized object. In a mouse, it’s a little bigger. It’s bean-sized in a rat, about the size of your little finger in a rabbit, and the size of your thumb in a bloodhound.”   Does that mean that our sense of smell is not very acute ?   Not exactly. While we may not have the olfactory range of other creatures, the receptors we do have are as sensitive as those of any animal. ___4___ A trained “nose”, such as that of a professional in the perfume business, can name and distinguish about 10,000 odors. Reed says that a perfume expert can sniff a modem scent that has a hundred different odorants in it, go into the lab, and list the ingredients. “In a modest amount of time, he comes back with what to you or me would smell like a perfect imitation of that perfume. It’s amazing.”   What happens to4 our sense of smell as we age ?   Many people continue to have good olfactory function as they get older. ___5___ Leopold says that smell is generally highest in childhood, stays the same from the teens through the 50s, and drops starting at about 60 for women and 65 for men. “The average 80-year-old is only able to smell things half as well as the average 20-year-old,” says Leopold.词汇： scent /sent/ n. 气味，香味petunia /p 'tju:ni / n. 喇叭花olfactory / l'f kt( )ri/ adj. 嗔觉的，味道的sniff /snif/ v. 嗅，闻，用力吸注释：1.    bring out：使……显出，使……变得明显2.    warn of：发出关于……的警告。warn sb. of sth.：警告某人某事3.    compare with：与……相比4.    happen to：发生于，发生在练习：A    These flowers have a rich spiciness that no other petunia has.B    Odors, or smells, can warn us about trouble.C    That’s not the rule, however.D    And smell tells us about people.E    We can also think, and we make conscious (and successful) efforts to tell the difference between one smell and another.F    A rat has some 10 million, a rabbit 20 million, and a bloodhound 100 million.
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解析1. D 根据后文提到的“我们能够根据气味收集到有关人的很多信息”可以推断此处答案是D选项。2. A 前文提到以紫喇叭花的香味举例，选项中只有A选项提到了喇叭花。3. F 前文提到人类和小鼠的嗅觉受体细胞数量，可以推断此处应介绍其他物种的嗅觉受体细胞数量。4. E 后文都在介绍人类可以区分味道的不同，所以此处E选项最符合原文意思。5. C 后文介绍了不是每个人都随着年龄的增长嗅觉能力不发生变化，所以此处C选项最符合原文。嗅觉入门 嗅觉除了能让我们感受到食物的气味外，还能做什么 美国约翰霍普金斯大学研究嗅觉的专家Randall Reed教授指出，气味能提供给我们关于位置，关于我们在哪儿，以及有关人的信息。“无论我们是否意识到，我们能根据气味收集到许多关于谁在我们身边的信息，”Reed讲道。即使还隔着一段距离，气味就能提醒我们注意很多麻烦：变质的食物，煤气泄漏，或是火灾。“它是一个很好的警告，”约翰霍普金斯大学的医生Donald Leopold说道。比方说，烤箱中有东西烧焦了，屋内的每个人都会知道。仅仅是简单的气味，嗅觉就会引起强烈的情感。比如说那种气味就是紫喇叭花。它的气味中有一种其他喇叭花没有的香味。现在我们想象一下，你的母亲在你3岁时就去世了，她曾经拥有一座花园。你不必去辨认那种气味或者有意识地回忆起你的母亲或者她的花园，只要是你闻到那种紫喇叭花的香味，你就会感到伤感。与动物相比，人类感知气味的能力有多强 那要取决于你所谓的“多强”是什么意思。我们人类的受体细胞很少：目前估计人类有大概500万个嗅觉受体细胞，差不多和一只小鼠的一样多。一只大鼠大约有1 000万个，一只兔子有2 000万个，一只寻血犬有1亿个。Reed谈到，在不同的物种中，受体细胞的数量和嗅觉的强弱大体是正相关的。“人的大脑中是几乎找不到嗅球的，它像豌豆般大小。小鼠的脑中，嗅球大一点。大鼠的脑中，嗅球有蚕豆那么大，兔子脑中的有你的小手指那么大，而寻血犬脑中的有拇指那么大。”这是不是就意味着我们的嗅觉不够敏锐呢 不完全是。尽管我们的嗅觉范围可能没有其他生物的那么广，但是我们已有的受体细胞和其他动物的一样敏感。我们也可以认为，我们在有意（并且成功地〕努力区别不同的气味。受过培训的鼻子，比如研究香水的专家的鼻子就能够区分1万种气味并说出其名字。Reed说，一个香水专家可以在闻完一种含有100种不同香料的现代香水后，走进实验室，列出这些成分。“一段时间过后，他调制出来的气味对于你我来说都是那种香水气味的完美复制，太不可思议了。”随着年龄的增长，我们的嗅觉会发生什么变化 许多人年龄增大时还会有很好的嗅觉能力。但并不都是这样。指出，一个人的嗅觉在儿童时最强，在青少年时期一直到50多岁都保持不变，女人通常从60岁、男人从65岁开始下降。“通常来说，80岁的人能闻到的东西是20岁的人能闻到的一半，”Leopold说道。
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