你或许会注意到,聚会的一群人中只要有一个人打了哈欠,其他的人也会接二连三地开始打哈欠,甚至你家的宠物狗狗也会被你的哈欠传染。人为什么会打哈欠,打哈欠又为什么会传染呢?
You know the feeling. It’s impossible to resist. You just need to yawn.
你知道这种感觉。那种冲动很难抗拒,你就是想打个哈欠。
A yawn consists of an extended gaping of the mouth followed by a more rapid closure.
打哈欠时,人们张大嘴巴,之后以更快的速度闭上嘴。
In mammals and birds, a long intake of breath and shorter exhale follows the gaping of the mouth, but in other species such as fish, amphibians and snakes there is no intake of breath.
哺乳动物和鸟类张嘴打哈欠会吸入一大口气,之后短暂呼气。但其他动物打哈欠时并不吸气,比如鱼类、两栖动物和蛇。
But why does it occur?
但哈欠是怎么来的呢?
In the past, people have had many hypotheses. As far back as 400 BC, Hippocrates thought yawning removed bad air from the lungs before a fever.
在过去,人们有很多假想。在公元前400年,古希腊名医希波克拉底认为,发烧之前,哈欠会把废气从肺部排出。
In the 17th and 18th century, doctors believed yawning increased oxygen in the blood, blood pressure, heart rate and blood flow itself.
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