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carrier
n。 带菌者
exterminate
v。 消灭
ironically
adv。 具有讽刺意味地
bequeath
v。 把。。。传给
pest
n。 害虫，有害动物
pestilence
n。 瘟疫
confine
n。 范围
domesticate
v。 驯养
参考译文
在澳大利亚移民初期，一些有创业精神的移民不明智地把欧洲兔子引进了澳大利亚。这种兔子在澳大利亚及新西兰没有天敌，因此便以兔子所特有的杂乱交配迅猛繁殖起来。整个澳洲兔子成灾。它们在地下打洞，吃掉本可以饲养数百万头牛羊的牧草，给澳洲大陆造成了毁灭性的破坏。科学家们发现，这种特殊品种的兔子（显然不包括别的动物）易患一种叫“多发性粘液瘤”的致命毒性疾病。通过让染上此病的动物在洞内乱跑，就可以使这种疾病在一个地区蔓延起来。后来又发现，有一种蚊子是传播这种疾病的媒介，能把此病传染给兔子。因此，世界上其他地方在设法消灭蚊子的时候，澳大利亚却在促使这种蚊子大量繁殖。蚊子把这种疾病扩散到整个澳洲大陆，效果甚佳，结果兔子的数目在为减少。后来，明显看出，兔子对这种疾病已产生了一定程度的免疫力，所以兔子不可能被完全消灭。但是，已有希望解决兔子所带来的问题。
具有讽刺意味的是，欧洲把这种兔子作为有害动物传给澳洲，而欧洲自己却染上了这种人为的瘟疫般的疾病。一位法国内科医生决定除掉自己庄园内的野兔子，于是引进了这种多发性粘液瘤疾病。然而，这种疾病并未被局限在他的庄园内，结果在整个法国蔓延开来。野兔在法国一般不被当作有害动物，而被视为打猎取乐的玩物和有用的食物来源。这种疾病又蔓延到了英国。在英国，野兔被当作有害的动物，可是家兔是赚钱的毛皮工业的基础，然而家兔同样易感染这种疾病。现在的问题是，人类能否控制住这种人为的疾病。
Lesson 18
Porpoises
海豚
First listen and then answer the following question。
听录音，然后回答以下问题。
What would you say is the main characteristic of porpoises？
There has long been a superstition among mariners that porpoises will save drowning men by pushing them to the surface； or protect them from sharks by surrounding them in defensive formation。 Marine Studio biologists have pointed out that； however intelligent they may be； it is probably a mistake to credit dolphins with any motive of lifesaving。 On the occasions when they have pushed to shore an unconscious human being they have much more likely done it out of curiosity or for sport； as in riding the bow waves of a ship。 In 1928 some porpoises were photographer working like beavers to push ashore a waterlogged mattress。 If； as has been reported； they have protected humans from sharks； it may have been because curiosity attracted them and because the scent of a possible meal attracted the sharks。 Porpoises and sharks are natural enemies。 It is possible that upon such an occasion a battle ensued； with the sharks being driven away or killed。
Whether it be bird； fish or beast； the porpoise is intrigued with anything that is alive。 They are constantly after the turtles； who peacefully submit to all sorts of indignities。 One young calf especially enjoyed raising a turtle to the surface with his snout and then shoving him across the tank like an aquaplane。 Almost any day a young porpoise may be seen trying to turn a 300…pound sea turtle over by sticking his snout under the edge of his shell and pushing up for dear life。 This is not easy； and may require two porpoises working together。 In another game； as the turtle swims across the oceanarium； the first porpoise swoops down from above and butts his shell with his belly。 This knocks the turtle down several feet。 He no sooner recovers his equilibrium than the next porpoise es along and hits him another crack。 Eventually the turtle has been butted all the way down to the floor of the tank。 He is now satisfied merely to try to stand up； but as soon as he does so a porpoise knocks him flat。 The turtle at last gives up by pulling his feet under his shell and the game is over。
RALPH NADING HILL Window in the Sea
New words and expressions 生词和短语
porpoise
n。 海豚
mariner
n。 水手
shark
n。 鲨鱼
formation
n。 队形
dolphin
n。 海豚科动物
unconscious
adj。 不省人事
beaver
n。 海狸
ashore
adv。 上岸
waterlogged
adj。 浸满水的
scent
n。 香味
ensue
v。 接着发生
intrigue
v。 引起兴趣
indignity
n。 侮辱
snout
n。 口鼻部
shove
v。 硬推
aquaplane
n。 驾浪滑水板
oceanarium
n。 水族馆
swoop
v。 猛扑
belly
n。 腹部
equilibrium
n。 平衡
butt
v。 碰撞
crack
n。 重击
参考译文
长期以来，海员中流传着一种迷信的说法，认为海豚会把快要淹死的人托到水面，救人性命；或在人们周围列队保护，使他们免遭鲨鱼伤害。海洋摄影室的生物学家指出，无论海豚多么聪明，认为它们有救人的动机可能是错误的。当它们偶尔把一个失去知觉的人推到岸边时，更大的可能是出于好奇或游戏，就像它们追逐被船首犁开的浪花一样。1928年，有人拍摄到了海豚像海狸一样把浸透水的床垫推上岸的情景。正如报道中所说，如果海豚保护人不受鲨鱼侵害，那么它们可能是出于好奇；而鲨鱼可能是闻到了可以美食一顿的香味。海豚和鲨鱼是天然仇敌，双方可能随之发生搏斗，搏斗结果是海豚赶走或咬死鲨鱼。
海豚对凡是活的东西都感兴趣，不管是鸟、是鱼，还是野兽。它们经常追逐海龟，海龟则温顺地忍受着各种侮辱。一只小海豚特别喜欢用鼻子把海龟推到水面，然后像滑水板一样把海龟从水池的这一边推到那一边。几乎每天都可以看到一只小海豚把鼻子顶入一只300磅重的海龟的硬壳下面，拼命地把它翻过来。这并非易事，可能需要两只海豚合伙干才行。在另一场游戏中，当海龟游过水族馆时，第一只海豚从上方猛扑下去，用腹部撞击龟壳。这一下子把海龟撞下去好几英尺。海龟刚恢复平衡，第二只海豚又冲过来猛击一下。这只海龟最终被撞到池底。此时的海龟，只要能站起来就满足了，但它刚站起来，就被一只海豚击倒。海龟终于屈服了，将4条腿缩进壳内。游戏到此结束。
Lesson 19
The stuff of dreams
话说梦的本质
First listen and then answer the following question。
听录音，然后回答以下问题。
What is going on when a person experiences rapid eye…movements during sleep？
It is fairly clear that sleeping period must have some function； and because there is so much of it the function would seem to e important。 Speculations about is nature have been going on for literally thousands of years； and one odd finding that makes the problem puzzling is that it looks very much as if sleeping is not simply a matter of giving the body a rest。 'Rest'； in terms of muscle relaxation and so on； can be achieved by a brief period lying； or even sitting down。 The body's tissues are self…repairing and self…restoring to a degree； and function best when more or less continuously active。 In fact a basic amount of movement occurs during sleep which is specifically concerned with preventing muscle inactivity。
If it is not a question of resting the body； then perhaps it is the brain that needs resting？ This might be a plausible hypothesis were it not for two factors。 First the electroencephalograph （which is simply a device for recording the electrical activity of the brain by attaching electrodes to the scalp） shows that while there is a change in the pattern of activity during sleep； there is no evidence that the total amount of activity is any less。 The second factor is more interesting and more fundamental。 Some years ago an American psychiatrist named William Dement published experiments dealing with the recording of eye…movements during sleep。 He showed that the average individual's sleep cycle is punctuated with peculiar bursts of eye…movements； some drifting and slow； others jerky and rapid。 People woken during these periods of eye…movements generally reported that they had been dreaming。 When woken at other times they reported no dreams。 If one group of people were disturbed from their eye…movement sleep for several nights on end； and another group were disturbed for an equal period of time but when they were no exhibiting eye…movements； the first group began to show some personality disorders while the others seemed more or less unaffected。 The implications of all this were that it was not the disturbance of sleep that mattered； but the disturbance of dreaming。
CHRISTOPHER EVANS The stuff of dreams from The Listener
New words and expressions 生词和短语
speculation
n。 推测
literally
adv。 确实
odd
adj。 奇特的
tissue
n。 组织
plausible
adj。 似乎有理的
hypothesis
n。 假说
electroencephalograph
n。 脑电图仪
electrode
n。 电极
scalp
n。 头皮
psychiatrist
n。 精神病学家
punctuate
v。 不时介入
jerky
adj。 急动的
disorder
n。 失调
implication
n。 表明
参考译文
很清楚，睡眠必然具有某种作用。睡眠占去那么多时间，所以其作用似乎还是很重要。人们对睡眠作用的种种猜测，确实有数千年之久。一项使人对这个问题感到困惑的奇怪的发现是，睡眠在很大程度似乎并不仅仅是为了使身体得到休息。“休息”，从使肌肉得到放松等方面来看，只要稍微躺一躺，甚至坐一坐就能达到。人体组织在一定程度上有自我修补和自我恢复的能力，有张有弛地连续活动时，其功能最佳。事实上，睡眠状态下仍有着基本的活动量，以防止肌肉活动停止。
如果睡眠的功能不是在于使身体得到休息，那么也许是让大脑得以休息？若不是下面两点，这种假使似乎是有道理的。第一点，脑电图记录仪（不过是一种把电极接到头皮上记录脑电活动的仪器）显示，人在睡眠时大脑活动的方式有变化，但没有迹象表明，其活动总量有任何减少。第二点更有意思，也更重要。前些年，美国一位精神病学者发表了一篇报告，报告中记录了眼球在睡眠时的活动情况。他指出，平常人的睡眠周期中不时伴有一阵阵奇怪的眼球队活动，这些活动有的飘忽而缓慢，有的急剧而快速。在眼球活动期间被叫醒的人都说自己在做梦；在其他期间叫醒他们，则说没有做梦。如果有两组人，一组人连续几夜在眼球队活动时被叫醒；另一组人也是连续几夜被叫醒，但是在眼球队没活动时被叫醒的。结果，第一组人开始出现性格失常，而第二组人似乎没受什么影响。这一切暗示我们：睡眠受到干忧没关系，而做梦受到干忧是有问题的。
Lesson 20
Snake poison
蛇毒
First listen and then answer the following question。
听录音，然后回答以下问题。
What are the two different ways in which snake poison acts？
How it came about that snakes manufactured poison is a mystery。 Over the periods their saliva； a mild； digestive juice like our own； was converted into a poison that defies analysis even today。 It was not forced upon them by the survival petition； they could have caught and lived on prey without using poison； just as the thousands of non…poisonous snakes still do。 Poison to a snake is merely a luxury； it enables it to get its food with very little effort； no more effort than one bite。 And why only snakes？ Cats； for instance； would be greatly helped； no running fights with large； fierce rats or tussles with grown rabbits just a bite and no more effort needed。 In fact； it would be an assistance to all carnivores though it would be a two…edged weapon when they fought each other。 But； of the vertebrates； unpredictable Nature selected only snakes （and one lizard）。 One wonders saliva into why Nature； with respect from that of others； as other on the blood。
In the conversion of saliva into poison； one might suppose that a fixed process took place。 It did not； some snakes manufacture a poison different in every respect from that of others； as different as arsenic is from strychnine； and having different effects。 One poison acts on the nerves； the other on the blood。
The makers of the nerve poison include the mambas and the cobras and their venom is called neurotoxic。 Vipers （adders） and rattlesnakes manufacture the blood poison； which is known as haemolytic。 Both poisons are unpleasant； but by far the more unpleasant is the blood poison。 It is said that the nerve poison is the more primitive of the two； that the blood poison is； so to speak； a newer product from an improved formula。 Be that as it may； the nerve poison does its business with man far more quickly than the blood poison。 This； however； means nothing。 Snakes did not acquire their poison for use against man but for use against prey such as rats and mice； and the effects on these of viperine poison is almost immediate。
JOHN CROMPTON The snake
New words and expressions 生词和短语
saliva
n。 唾液
digestive
adj。 助消化的
defy
v。 使不可能
analysis
n。 分析
prey
n。 被捕食的动物
fierce
adj。 凶猛的
tussle
n。 扭打
carnivore
n。 食肉动物
vertebrate
n。 脊椎动物
lizard
n。 蜥蜴
concoct
v。 调制
potency
n。 效力
conversion
n。 转变
arsenic
n。 砒霜
strychnine
n。 马钱子碱
mamba
n。 树眼镜蛇
cobra
n。 眼镜蛇
venom
n。 毒液
neurotoxic
adj。 毒害神经的
viper
n。 蝰蛇
adder
n。 蝮蛇
rattlesnake
n。 响尾蛇
haemolytic
adj。 溶血性的
viperine
adj。 毒蛇
参考译文
蛇是怎样产生毒液的，这是一个谜。蛇的唾液本来和我们人的消化液一样柔和，但经过漫长的时间，演变成了今天仍无法分析清楚的毒液。毒液不是生存竞争强加给它们的，它们也可以不用毒液捕捉动物而生存，就像今天成千上万的无毒蛇那样。毒液对毒蛇来说只不过是一种舒适生存的优越手段，它使蛇不用费多大力气就能捕获到食物，轻咬一口即可。为什么只有蛇才有毒液呢？譬如说，如果猫有毒液，那对猫会大有帮助，它就不必再和又大又凶的老鼠边跑边博斗了，也不必再和大兔子扭斗了，只要咬一口，就不必再费大力气。因此，任何食肉动物有了毒液，都能从中获益。不过，当它们相互撕打时，毒液就成了利弊参半的武，可以杀死对方，也可以被对方的毒液杀死。然而，在脊椎动物中，大自然神秘模测地只选择了蛇（还有一种蜥蜴），人们弄不清楚大自然为什么在某些蛇的身上调制出如此高效的毒液来。
人们可能认为，唾液转变成毒液，其中有固定的程序。其实没有。有些蛇产生的毒液也在各方面与另外一些毒蛇产生的毒液不同，就�