有時候，當我們從很熱的地方進入很冷的地方時，皮膚上會感到一陣發(fā)緊，接著出現一些密密麻麻的顆粒，就像雞的皮一樣，這就是人們常說的“雞皮疙瘩”。英語中把這種小疙瘩叫做 goose bumps。為什么我們的皮膚受到刺激就會起雞皮疙瘩呢？下面這篇文章將為您解釋一下。

Goose bumps are a vestige from the days when humans were covered with hair.

When it's hot and you need to cool down, little muscles at the base of each hair relax. Your hair becomes relaxed. Your sweat glands pump out body heat in sweat. Your blood vessels get big to take more heat to the skin to get rid of it. When it's cold, the arrector muscle pulls the hair up. The duct to the sweat glands gets small to conserve heat. Our blood vessels also get small to save heat.

Hair standing up doesn't make very good insulation for we don't have enough fur for that. Humans don't have very much hair on their bodies anymore. Millions of years ago, humans probably did. And that hair standing on end helped keep people warmer. Those little muscles we have on the end of each hair still work. They still make goose bumps.

Cold is not the only thing that can cause our hair to stand on end. Fear or anger can cause the same reflex. The same is true for other mammals. You'll notice that on a cat or dog. Their fur gets bigger when they're angry or afraid.

vestige: 殘余，痕跡

gland：腺

muscle：立毛肌

conserve：貯藏

insulation：隔熱

reflex：反應

（英語點津 Annabel 編輯）