1.When we talk about ears,we usually mean the oddly wrinkled appendages on the side of our heads.2.We are aware that at the end of the central hole in this outer ear there is something called the middle ear,with an eardrum and a few little bones.Even deeper lies the inner ear,the organ with which we "hear".3.Animals such as dogs and cats also have conspicuous outer ears,but few of us probably ever stopped to think whether there might be such a thing as a middle and inner ear beneath those point tips.Yet,we know very well that these animals hear.4.Birds are even more mysterious,because here we do not even see an outer ear.The same is true to still a larger degree of such animals as frogs and fished; although in the frog we can least see an eardrum.5.Again,at one time or another,you may have found that all such animals hear.Hunters know that birds are attracted by artificial calls,and fishermen emphasize that you should be as quite as possible if you don't want to go home empty handed.And if you even hunted frogs in your childhood,you know how softly you had to tread!Moreover,it seems absurd that birds should sing and frogs croak,if the could not even hear their own voices.6.By direct observations and many experiments,biologists have discovered that practically all animals have some sense of hearing or vibration.Earthworms feel vibrations in the soil,fish can be trained to respond to certain tones,male mosquitoes are attracted by the sound of the female,and frogs will respond to a tape recording of their own voices.7.The inner ears is composed of delicate membranes which bear dense patches of specialized cells called maculae.Each of these collections of cells can carry a message to the brain.What message is carried by a macula depends upon how it is affected.The message which is carried kind of tadpole can tell the depth of the water it is swimming in by the pitch of a tone which is produced by its own lungs.8.In the human and all other mammals,the macula has developed into an organ which easily be seen.This organ is called the cochlea.This spiral shaped organ contains the macula itself and it is called "Organ of Corti" after its discoverer.If you have ever seen a snail shell,you know how a cochlea looks.9.When sound waves enter the cochlea,which is really a coiled around.They set a membrane into a back forth motion and cause a new wave.This is something like the way in which high and low sounds are produced by a flute or whistle.The high sounds are produced when the air is prevented by the holes from going though,while the low sounds are produced by allowing more of the air to pass.All this is what produces the differences by how much the membrane is cause to move.10.Weather or not hearing is really produced in all animals by the effect of pressure is not definitely know by scientists as yet.We do know,however,that nature has set up some very delicate hearing mechanisms for its creatures.Scientists must explore much further for more knowledge about how animals use their ears.1.当我们提到耳朵时,通常是指那个长在我们头部两侧的奇特的褶皱的附属肢体.
2.我们知道,在外耳中孔的底部有东西称为中耳,它由一个耳鼓和一些小骨骼构成.而真正能使我们“听”的器官在更深处的内耳.
3.诸如猫和狗这样的动物也有引人注目的外耳,但很少人能够停下来去想,在竖立的尖儿下面,是否有类似于中耳和内耳的东西.但是我们很清楚地知道这些动物都能够听到.
4.鸟类甚至更为神秘,因为我们甚至看不到它有一个外耳.还有很大数量的动物如青蛙和鱼类也是如此.虽然我们至少可以看到青蛙有一个耳鼓.
5.此外,你可能曾经发现所有的这些动物都在听.猎人们知道鸟类会被人造的声音所吸引,渔夫们则强调,如果你不想空手而归的话就要尽可能的安静.如果你童年抓过青蛙,你应该知道要多么轻柔的走动.说是在的,青蛙在叫,鸟儿在唱,如果它们甚至听不到自己发出的声音,岂不荒谬.
6.通过直接观察和许多试验,生物学家已经发现,实际上所有的动物都具有某种听觉或震动感.蚯蚓在土壤里能感受到震动,鱼类可以训练的对特定的音调有反映,雄性蚊子可以被雌性蚊子的声音所吸引,青蛙对他们自己声音的录音有反映.
8.对于人类和其他所有哺乳动物来说,MACULAE已经进化成为一种很容易看见的器官,这种器官称为“耳蜗”.这一螺旋形的器官包括了MACULAE本身,以及后来被其发现者称为“CORTI”的器官.如果你看到过蜗牛的壳,你就知道耳蜗的形象了.
9.当声波进入耳蜗这条盘旋的管道,它令薄膜前后移动并且产生新的波动.这种方式类似于长笛或是勺子所产生的高低音.当洞穴被阻挡导致空气不能通过通道时就产生高音,而有更多空气通过通道时就产生低音.这些造成了高音和低音的不同,而声音的大小则明显的决定于耳膜运动.