蓝色血液的神话

I remember when I was young, a science teacher captivated our class one day with the idea that horseshoe crabs have blue blood, which is indeed harvested for medical purposes. Then we were told that we too sometimes have blue blood, in our veins, when our blood has delivered its supply of oxygen to our organs and tissues. It remains blue, we were told, until passing through the heart and past the lungs, where it acquires oxygen and turns red again. But is it true? After all, our veins do look blue.

记得我小的时候，一名科学课老师用马蹄蟹有蓝色血液的想法迷住了我们整个班的同学，当然这确实是为了医学目的而获得的。然后我们被告知，我们有时也有蓝色血液，比如将氧气供应到器官和组织的静脉血液。老师告诉我们，静脉血液会一直保持蓝色，直到穿过心脏并经过肺部，在那里它获得氧气并再次变成红色。但这是真的吗？毕竟，我们的静脉看起来是蓝色的。

Turns out, it’s a complete myth. Although veins do carry deoxygenated blood back to the heart, the blood merely looks a darker shade of red. It doesn’t turn blue at all. Still, the myth persists.

事实证明，这完全是一个神话。虽然静脉确实把脱氧的血液带回心脏，但血液看起来仍只是深红色，完全没有变回蓝色。不过，神话仍然存在。

The reason blood is red is, it contains hemoglobin. This iron-rich protein carries oxygen throughout the bloodstream. Anything with a lot of iron gives off a red hue. Consider the red planet—Mars, which has an iron-rich dust covering its surface. And when iron rusts (iron oxide) it turns an orangey-red.

血液之所以是红色，是因为它含有血红蛋白，这种富含铁的蛋白质在血液中运输氧气。任何含铁丰富的事物都会呈现出红色的色调，比如红色的火星。火星表面覆盖着一层富含铁的尘埃。当铁生锈成为氧化铁时，它会变成橙红色。

Oxygenated blood is bright red, while deoxygenated blood appears darker. Have you ever donated blood or had it taken for a blood test? You’ll notice they puncture a vein, usually in the arm, and still it comes out red. So why do veins look blue? This has to do with how light is reflected and scattered as it passes through your skin. 

含氧血呈鲜红色，脱氧血呈暗红色。你是否曾经献血或验血呢？你会发现，即使被刺的位置通常是手臂上的静脉，但血液仍然是红色的。所以，为什么静脉看起来是蓝色的？这与光透过皮肤时的反射和散射有关。

You might remember from studying the electromagnetic spectrum that blue and red light have different wavelengths. As light passes through your skin, some of it gets absorbed, some of it scattered, and some reflected back to you. Since blue light reflects back better than red, our veins below our skin look blue. If you previously believed the blue blood myth, don’t feel bad. A lot of well-educated people have.

你可能还记得在研究电磁光谱时，蓝色和红色的光有不同的波长。当光线穿过你的皮肤时，其中的一些被吸收，一些被散射，一些反射到你身上。由于蓝光反射比红色好，所以我们皮肤下面的静脉看起来是蓝色的。如果你以前相信蓝血神话，也不要难过，毕竟很多受过良好教育的人也曾这样。

Besides horseshoe crabs and octopi, lobsters and other crustaceans, and squid also have blue blood. That’s because instead of the respiratory protein hemoglobin, their blood uses hemocyanin to carry oxygen. Hemocyanin contains copper instead of iron. If you’ve ever seen a copper penny rust, you’ll notice it turns green. When mixed with oxygen however, it turns blue. There’s another, rarer color of blood in the animal kingdom.

除了马蹄蟹和章鱼外，龙虾和其他甲壳类动物，还有鱿鱼也有蓝血。这是因为他们的血液不是用血红蛋白呼吸，而是用血蓝蛋白运送氧气。血蓝蛋白含有的元素是铜而不是铁。如果你见过铜锈，你会注意到它变绿的样子。然而，当与氧气混合时，它会变成蓝色，这是动物王国里另一种稀有的血色。

The skink—a type of lizard, has green blood. This is due to the buildup of a substance called biliverdin, which is a byproduct of the processes of the liver. Humans have it too. But our bodies pass it through the intestines and out the digestive tract. Since it doesn’t pass through a skink, it builds up in their blood instead, turning it green.

石龙子是一种有绿色血液的蜥蜴。这是由于一种叫做胆绿素的物质的积累缘故，这种物质是肝脏过程的副产物，在人体中也存在。但是在我们的身体里，胆绿素通过肠道和消化道排出体外，而不是像在蜥蜴体内那样在血液中变成绿色。