新托福阅读材料：NostrilsandRoses

　　众所周知，我们有左右两个肺脏，但可能很少人知道，每一侧肺脏都是由其同侧相应的鼻孔控制的。

　　因此如果一个鼻孔堵塞，两侧的肺就会产生竞争，让人觉得难受、呼吸不畅。不仅如此，专关家认为两个鼻孔还能使呼吸运动更有效，进而推进整个机体的新陈代谢。用两个鼻孔透气使得每一个鼻孔可以轮换稍事休息，如果只用一个鼻孔透气，3小时就会感到疲劳。

　　两个鼻孔的生理结构有助于睡眠。在8小时以上的睡眠中如果保持一种睡姿不变，由于重力作用与站姿时相比发生了变化，一侧的鼻孔通常会闭塞。

　　因此，我们用两个鼻孔透气可以睡得更放松。由于睡眠中人对氧气的需求量减少，即使一个鼻孔暂时不通，只有另一个呼吸也不会造成呼吸不畅。

　　今天我们就一起了解一下两个鼻孔的重要性吧。

　　Take a Look in the mirror and ask yourself this: why do I have two nostrils. Two eyes, sure. Two ears, ok. But why two nostrils? Wouldn’t one, big nostril do just as well?

　　Actually, no. First, one giant nostril would look really weird. And second, although they may look identical, each nostril actually smells a bit differently. For most people, nostrils take turns swelling and shrinking, meaning that at any given moment the rate at which a nostril inhales is not equal.

　　Let’s say you’re taking a walk and stop to sniff a rose. Your swollen nostril inhales the tiny, microscopic particles released by the rose at a relatively slower pace than the normal nostril, which inhales at a normal clip. This is important since chemicals that enter your nose and create smell, including rose particles, come in two basic types: those that dissolve slowly and those that dissolve more quickly.

　　In order for slow-dissolving rose chemicals to really work they have to enter the nose at a leisurely pace and kind of settle down. If they’re rushed in on a fast stream of air too many pass right through the nose and don’t contribute to that unique, rosy smell. The rose chemicals that dissolve quickly, meanwhile, like to charge in and spread out fast in order to really pack a punch. Since they inhale at different speeds, your nostrils allow both kinds of rose chemicals to do their thing.

　　So a rose may be a rose, but in order to really smell one you need two nostrils. One big one just won’t do.