Water is so vital to us that it is easy to overlook that all but the smallest fraction of the water on Earth is poisonous to us—deadly poisonous—because of the salts within it.
水对我们太重要了，因此我们不容易注意到，地球上绝大部分的水对我们来说都是有毒的——而且毒得厉害，因为里面含有盐。
We need salt to live, but only in very small amounts, and seawater contains way more— about seventy times more—salt than we can safely metabolize. A typical liter of seawater will contain only about 2.5 teaspoons of common salt—the kind we sprinkle on food—but much larger amounts of other elements, compounds, and other dissolved solids, which are collectively known as salts. The proportions of these salts and minerals in our tissues is uncannily similar to seawater—we sweat and cry seawater, as Margulis and Sagan have put it—but curiously we cannot tolerate them as an input.
有盐我们才能活下去，但只要很小的量。海水里含盐量太大——大了大约70倍——我们无法平安无事地将其新陈代谢。1升海水里只含有大约2.5茶匙普通的盐——我们撒在食物上的那种盐，但还含有大量的其他元素、化合物和别的已经溶解的团体，这一些通称为盐。盐和矿物质在我们肌体组织里的比例，与在海水里的比例也差不多——正如马吉利斯和萨根说的，我们出的汗是海水，流的泊是海水。但是，说来也怪，我们却无法忍受外来的盐。
Take a lot of salt into your body and your metabolism very quickly goes into crisis. From every cell, water molecules rush off like so many volunteer firemen to try to dilute and carry off the sudden intake of salt. This leaves the cells dangerously short of the water they need to carry out their normal functions. They become, in a word, dehydrated. In extreme situations, dehydration will lead to seizures, unconsciousness, and brain damage. Meanwhile, the overworked blood cells carry the salt to the kidneys, which eventually become overwhelmed and shut down. Without functioning kidneys you die. That is why we don't drink seawater.
要是把大量盐摄人自己体内，你的新陈代谢很快会陷入危机。每个细胞里的水分子都会匆匆离去，像是许多志愿消防员急着要去稀释和冲走突然增加的盐分那样。结果，细胞严重缺水、无法正常运转。简而言之，细胞脱水了。在极端情况下，脱水会造成疾病发作、昏迷和大脑损伤。与此同时，劳累过度的血细胞会把盐输送到肝脏，最后肾脏会负担过重，停止运转。要是肾脏不能正常运转，你就会死去。这就是你不能饮用海水的原因。
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