為什麼貓的眼睛在黑暗中發光？

Cats and many other animals， including most dogs， can reflect light from their eyes。That‘s why cats’ eyes will usually shine brightly in photos taken in a dimly lit room or glow when illuminated in the dark by a flashlight or a car‘s headlights。

貓和許多其他的動物，包括狗在內。他們的眼睛可以反射光線。這就是為什麼貓的眼睛經常在照相時、暗的房間裡或者有手電筒和車燈照耀時發出明亮的光線。

Species whose eyes glow have evolved to see better in low light because they either forage or need to look out for predators throughout the night， or they do most of their hunting at dawn and dusk。In fact， domesticated cats can see in conditions that are only 16% as bright as what people require。

眼睛發光的物種已經進化，在弱光下看得更好的視線。他們要麼覓食，要麼需要整夜留心捕食者。或者在黎明或者黃昏的時候捕獵。實際上家貓的視力所需的亮度只有人類所需亮度的16%。

Cats accomplish this because their pupils – the openings that appear black in the middle of their eyes that widen and narrow in response to light conditions – are special。Pupils operate like windows， with bigger ones letting more light into the eye。And a cat’s pupils can become up to 50% larger than human pupils in dim light。They also have a higher number of a specific type of light-sensing cell in the back of their eyes than we do。These cells， called rods， catch low-level light。

貓實現這是因為他們的瞳孔，在它們眼睛中間黑色的能夠放大縮小的開口對光亮的迴應功能是特殊的。瞳孔的運轉就像一扇窗戶，隨著更大的開啟帶來更多的光進入眼睛。貓的瞳孔能夠在昏暗光下比人類大百分之50。他們還比我們擁有更多數量的特殊種類的感光細胞在它們眼睛的背後。這些細胞叫做杆細胞，能夠捕捉低亮度的光。

The tapetum lucidumIn

addition to having large pupils and lots of rods， cats have something people don‘t： a tapetum lucidum， a Latin medical term that translates to “bright or shining tapestry。” The tapetum lucidum is also known as “eyeshine。”

除了大的瞳孔和許多的杆外，貓咪還有人類沒有的東西：透明絨被，這是一個拉丁語醫學術語，翻譯成“明亮的或閃亮的掛毯”。透明絨被也被稱為“擦眼油”。

It’s located in the back of the eye behind the retina – a thin layer of tissue that receives light， converts the light to an electrical signal and sends this signal to the brain to interpret the image。

它位於眼睛後方，視網膜的後面，視網膜是一層薄薄的組織，用來接收光亮，改變光亮為電能的訊號並且將這種訊號傳給大腦去解釋影象。

A cat‘s tapetum lucidum is made up of cells with crystals that， like a mirror， reflect light back to the retina。This gives the retina a second chance to absorb more light。

貓的透明絨毛膜是由帶有晶體的細胞組成的，晶體像鏡子一樣，將光線反射回視網膜。這給了視網膜第二次吸收更多光線的機會。

The feline tapetum lucidum is special because its reflective compound is riboflavin， a type of vitamin B。 Riboflavin has unique properties that amplify light to a specific wavelength that cats can see well， which greatly increases the sensitivity of the retina to low light。

貓咪絨毛很特別，因為它的反射化合物是核黃素，一種維生素B。Riboflavin具有獨特的特性，將光放大到貓咪可以清楚看到的特定波長，這大大增加了視網膜對弱光的敏感度。

In cats， the tapetum most often glows yellow-green or yellow-orange， but the color varies， just like their irises – the colorful part of their eye， which can be green， yellow， blue or golden。

貓的絨毛膜通常發出黃綠色或黃塵的光，但顏色會有所不同，就像他們的虹膜一樣，它們的顏色的五顏六色的部分可以是綠色，黃色，藍色或金色。

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