被紙割傷為什么那么疼？真是十指連心？

Paper seems completely harmless, but deployed properly, it can be a serious weapon: paper cuts are just the worst.

紙看起來無害，但合理使用的話，它也能成為犀利的武器：最嚴重的狀況就是被紙割傷。

It’s all to do with nerve endings. To start with, there are lots more pain receptors embedded in your fingertips than almost anywhere else in your body. So while a paper cut on your arm, or thigh, or ankle might still be annoying, it would probably be more trivial than the intense fiery quality that finger-based paper cuts tend to have.

這跟神經(jīng)末梢有關。首先，指尖的痛覺感受器比其他任何身體部位要多得多。所以，雖然紙割傷胳膊、大腿、腳踝也很疼，但也要比割傷手指那種火辣辣的疼痛感要輕得多。

This actually makes a good deal of evolutionary sense. Fingertips are how we explore the world, how we do small delicate tasks. So it makes sense that we have a lot of nerve endings there. It’s kind of a safety mechanism.

這其實是非常符合進化論的。我們用指尖來探索世界，做精細工作，所以指尖就該有很多神經(jīng)末梢，這是一種安全機制。

To the naked eye, it might seem as if a paper's edge is fairly straight and smooth. But if you were to zoom in, you’d find that paper is more akin to a saw than to a blade.

肉眼看著好像紙的邊緣很直很平，但如果你放大看，會發(fā)現(xiàn)紙更像鋸而非刀片。

And paper cuts are typically shallow – but not too shallow. They’re deep enough to get past the top layer of the skin, otherwise they wouldn’t hurt. The top layer of skin has no nerve endings. But they don’t slice that deep into your body, which is perhaps why it’s puzzling that they should hurt so much. A deeper wound would result in bleeding. The blood would clot and a scab would develop, beneath which the skin could go about healing free from the continuedassault of the outside world. But the shallow wound of a paper cut doesn't offer such protection.

被紙割出的傷口淺，但也不是太淺。傷口深入到皮膚表層之下，否則就不疼了，皮膚表層沒有神經(jīng)末梢。但他們還不太深，這可能就是為什么人們會疑惑怎么這么疼，更深的傷口會引起出血，血會凝結，然后結痂，下面的皮膚可以不受外界干擾自行修復。但紙割出的淺的傷口就沒有這種保護。

Without the cushion of blood, pain receptors are left exposed to the elements, and unless you quickly bandage your paper cut, those neurons will keep on sending the alarm bell. That, after all, is their job.

沒有血液的這種保護作用，痛覺感受器被暴露在自然環(huán)境之中，除非快速包扎傷口，否則神經(jīng)元會一直傳送警報，畢竟這就是它們的工作。

Unfortunately, each of us is going to face the prospect of enduring a few paper cuts as we go about our lives. Luckily, a thousand paper cuts would really really hurt, but it probably wouldn’t kill you.

不幸的是，我們在生活中都會被紙割傷幾次。但幸運的是，被紙割傷一千次可能真的非常非常疼，但也死不了。