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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.

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.

練習(xí)：

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.

參考答案：

1. D 2. A 3. F 4. E 5. C

嗅覺入門

嗅覺除了能讓我們感受到食物的氣味外，還能做什么？

美國約翰霍普金斯大學(xué)研宄嗅覺的專家Randall Reed教授指出，氣味能提供給我們關(guān)于位 置，關(guān)于我們?cè)谀膬?，以及有關(guān)人的信息。“無論我們是否意識(shí)到，我們能根據(jù)氣味收集到許 多關(guān)于誰在我們身邊的信息，” Reed講道。

即使還隔著一段距離，氣味就能提醒我們注意很多麻煩：變質(zhì)的食物，煤氣泄漏，或是火 災(zāi)。“它是一個(gè)很好的警告，”約翰霍普金斯大學(xué)的醫(yī)生Donald Leopold說道。比方說，烤箱 中有東西燒焦了，屋內(nèi)的每個(gè)人都會(huì)知道。

僅僅是簡單的氣味，嗅覺就會(huì)引起強(qiáng)烈的情感。比如說那種氣味就是紫喇機(jī)花。它的氣味 中有一種其他喇叭花沒有的香味?，F(xiàn)在我們想象一下，你的母親在你3歲時(shí)就去世了，她曾經(jīng)擁有一座花園。你不必去辨認(rèn)那種氣味或者有意識(shí)地回憶起你的母親或者她的花園，只要 是你聞到那種紫喇叭花的香味，你就會(huì)感到傷感。

與動(dòng)物相比，人類感知?dú)馕兜哪芰τ卸鄰?qiáng)？

那要取決于你所謂的“多強(qiáng)”是什么意思。我們?nèi)祟惖氖荏w細(xì)胞很少：目前估計(jì)人類有大 概500萬個(gè)嗅覺受體細(xì)胞，差不多和一只小鼠的一樣多。一只大鼠大約有1000萬個(gè)，一只兔 子有2 000萬個(gè)，一只尋血犬有1億個(gè)。

Reed談到，在不同的物種中，受體細(xì)胞的數(shù)量和嗔覺的強(qiáng)弱大體是正相關(guān)的。“人的大腦 中是幾乎找不到嗔球的，它像豌豆般大小。小鼠的腦中，嗔球大一點(diǎn)。大鼠的腦中，嗔球有 蠶豆那么大，兔子腦中的有你的小手指那么大，而尋血犬腦中的有拇指那么大。”

這是不是就意味著我們的嗔覺不夠敏銳呢？

不完全是。盡管我們的嗅覺范圍可能沒有其他生物的那么廣，但是我們已有的受體細(xì)胞和 其他動(dòng)物的一樣敏感。我們也可以認(rèn)為，我們?cè)谟幸猓ú⑶页晒Φ亍撑^(qū)別不同的氣味。 受過培訓(xùn)的鼻子，比如研宄香水的專家的鼻子就能夠區(qū)分1萬種氣味并說出其名字。Reed說， 一個(gè)香水專家可以在聞完一種含有100種不同香料的現(xiàn)代香水后，走進(jìn)實(shí)驗(yàn)室，列出這些成 分。“一段時(shí)間過后，他調(diào)制出來的氣味對(duì)于你我來說都是那種香水氣味的完美復(fù)制，太不可 思議了。”

隨著年齡的增長，我們的嗔覺會(huì)發(fā)生什么變化？

許多人年齡增大時(shí)還會(huì)有很好的嗅覺能力。但并不都是這樣。指出，一個(gè)人的嗔覺在兒童 時(shí)最強(qiáng)，在青少年時(shí)期一直到50多歲都保持不變，女人通常從60歲、男人從65歲開始下降。

“通常來說，80歲的人能聞到的東西是20歲的人能聞到的一半Leopold說道。