空气是维持生命所不可缺少的。一个人三、五天不吃饭还能活着,但十多分钟不呼吸空气就会憋死。我们试将一只小白鼠放进一只小玻璃瓶里,将瓶口用橡皮塞塞紧;将另一只小白鼠放进另一个小玻璃瓶,让瓶口敞开。第二天检查,封闭的瓶内,小白鼠死了;敞口瓶内,小白鼠仍然活蹦乱跳。小白鼠为什么会死呢?因为鼠的呼吸将瓶中氧气消耗了,二氧化碳增多了。为什么另一只小白鼠还活着 Air is indispensable to life. A person three or five days can live without food, but more than ten minutes without breathing air will suffocate. We will put a mouse into a small glass bottle, the bottle with a rubber stopper plug; the other mouse into another small glass bottle, so that the bottle open. The next day check, closed the bottle, the mouse died; open bottle, the mouse is still alive. Why mice die? Because the breath of rats consumed oxygen in the bottle, carbon dioxide increased. Why is another mouse alive?