Salt is as necessary to life as water. In many areas of Africa people once drank the urine of animals because they had no other source of salt. Without salt, human beings die.

    The human body demands that the amount of salt in the blood always stay the same. When the body does not get enough salt, it protects itself by letting less salt leave the body in. urine and sweat. But it cannot reduce this output to zero. Some salt is always escaping. On a completely saltless diet, like that of some people in Africa, the body steadily loses small amounts of salt through the kidneys and sweat glands. It then tries to adjust to this loss by speeding up its secretion of water. In this way, the body attempts to keep the amount of salt in the blood at the necessary level. The result is a slow drying up of body and, finally, death. The person dies of thirst.

    In cases where there is little or no water to drink, the body tries to do the opposite thing.
Again, it must keep the salt level in the blood constant.Because it has little water, it attempts to stop water from leaving the body and to increase its secretion of salt. But, as with the escaping salt, it cannot be completely successful. Some water still leaves and the person eventually dies of thirst. In short, the body's normal needs for salt and for water are both parts of the same important need to keep the salt level in the blood constant.

和水一樣蟀伸，鹽也是生命不可缺少的物質(zhì)僵闯。非洲很多地區(qū)的人都曾經(jīng)飲用過動物的尿液泌类，因?yàn)樗麄儧]有別的鹽的來源癞谒。沒有鹽人們就會死亡。

人類的身體要求血液中鹽分的數(shù)量總是保持一致刃榨，當(dāng)身體沒有足夠鹽分的時(shí)候弹砚，它會通過讓尿液和汗液排放更少的鹽分來保護(hù)自己。但是它不能把輸出量減少為零枢希。一些鹽分總會流失掉桌吃。完全沒有鹽分的飲食，就像一些生活在非洲的人晴玖，他們的身體會通過腎腺和汗腺緩慢地失去少量的鹽分读存，然后再通過加速分泌水來調(diào)節(jié)這個(gè)損失。身體通過這種方式盡量讓血液中的鹽量保持在一個(gè)必要的水平上呕屎。這樣調(diào)節(jié)的結(jié)果就是人們的身體慢慢地干涸让簿，最后死去，也就是渴死秀睛。

一旦人們有很少或沒有水喝尔当，身體就會做出相反的反應(yīng)。它必須保持血液中鹽分的穩(wěn)定蹂安。因?yàn)閹缀鯖]有水分的時(shí)候椭迎，身體會試圖阻止水離開它并且增加鹽分的分泌。但是由于要流失鹽分田盈，也不能完全成功地阻止水分離開畜号。一些水還是會流失，最終導(dǎo)致人們渴死允瞧。簡而言之简软，身體正常需要的鹽分和水分對于保持血液中鹽分的水平不變是同樣重要的蛮拔。