新概念英语第四册Lesson 20 Snake poison

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 saliva¹, 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 competition; they could have caught and lived on prey² 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 tussles⁴ 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 lizard⁵). One wonders saliva into why Nature, with respect from that of others, as other on the blood.
In the conversion⁶ of saliva into poison, one might suppose that a fixed⁷ process took place. It did not; some snakes manufacture a poison different in every respect from that of others, as different as arsenic⁸ is from strychnine, and having different effects. One poison acts on the nerves, the other on the blood.
The makers⁹ of the nerve poison include the mambas and the cobras and their venom¹⁰ is called neurotoxic. Vipers¹² (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 primitive¹⁴ 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 viperine¹⁵ poison is almost immediate¹⁶.
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
tussle³
n. 扭打
carnivore
n. 食肉动物
vertebrate
n. 脊椎动物
lizard
n. 蜥蜴
concoct¹⁷
v. 调制
potency¹⁸
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
viper¹¹
n. 蝰蛇
adder¹³
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，就像砒霜不同于马钱子碱一样。不同毒蛇产生的毒液产生的效果不同，一种毒液作用于神经，另一种毒液作用于血液。
产生神经毒液的蛇有一种非洲树眼镜蛇和眼镜蛇，它们的毒液称为神经毒素。蝰蛇（蝮蛇）和响尾蛇产生血液毒素，称为溶血性毒液。这两种毒液都很可怕，但溶血性毒液尤其厉害。据说，神经毒液在两种毒液中是较为原始的一种，而溶血性毒液，打个比方说，是根据改良配方生产的一种较新的产品。不过，神经毒辣液比溶血性毒液在人身上起作用快得多。但是，这没有什么关系，因为蛇有毒液不是用来对付人的，而是对付它的猎物，诸如鼠类，毒液对这些猎物会立刻起作用。
 

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1 saliva   

n.唾液，口水

参考例句：

• He wiped a dribble of saliva from his chin.他擦掉了下巴上的几滴口水。
• Saliva dribbled from the baby's mouth.唾液从婴儿的嘴里流了出来。

2 prey   

n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨

参考例句：

• Stronger animals prey on weaker ones.弱肉强食。
• The lion was hunting for its prey.狮子在寻找猎物。

3 tussle   

n.&v.扭打，搏斗，争辩

参考例句：

• They began to tussle with each other for the handgun.他们互相扭打起来，抢夺那支手枪。
• We are engaged in a legal tussle with a large pharmaceutical company.我们正同一家大制药公司闹法律纠纷。

4 tussles   

n.扭打，争斗( tussle的名词复数 )

参考例句：

• They need no running fights with large, fierce rats or tussles with grown rabbits. 它们不必奔跑着与大又凶的老鼠搏斗了，也不必跟大兔子扭斗了。 来自辞典例句
• The magazine has had a series of tussles with Asian governments. 该杂志曾与亚洲多国政府发生争执。 来自互联网

5 lizard   

n.蜥蜴，壁虎

参考例句：

• A chameleon is a kind of lizard.变色龙是一种蜥蜴。
• The lizard darted out its tongue at the insect.蜥蜴伸出舌头去吃小昆虫。

6 conversion   

n.转化，转换，转变

参考例句：

• He underwent quite a conversion.他彻底变了。
• Waste conversion is a part of the production process.废物处理是生产过程的一个组成部分。

7 fixed   

adj.固定的，不变的，准备好的；(计算机)固定的

参考例句：

• Have you two fixed on a date for the wedding yet?你们俩选定婚期了吗？
• Once the aim is fixed,we should not change it arbitrarily.目标一旦确定，我们就不应该随意改变。

8 arsenic   

n.砒霜，砷；adj.砷的

参考例句：

• His wife poisoned him with arsenic.他的妻子用砒霜把他毒死了。
• Arsenic is a poison.砒霜是毒药。

9 makers   

n.制造者，制造商（maker的复数形式）

参考例句：

• The makers of the product assured us that there had been no sacrifice of quality. 这一产品的制造商向我们保证说他们没有牺牲质量。
• The makers are about to launch out a new product. 制造商们马上要生产一种新产品。 来自《简明英汉词典》

10 venom   

n.毒液，恶毒，痛恨

参考例句：

• The snake injects the venom immediately after biting its prey.毒蛇咬住猎物之后马上注入毒液。
• In fact,some components of the venom may benefit human health.事实上，毒液的某些成分可能有益于人类健康。

11 viper   

n.毒蛇；危险的人

参考例句：

• Envy lucks at the bottom of the human heart a viper in its hole.嫉妒潜伏在人心底，如同毒蛇潜伏在穴中。
• Be careful of that viper;he is dangerous.小心那个阴险的人，他很危险。

12 vipers   

n.蝰蛇( viper的名词复数 )；毒蛇；阴险恶毒的人；奸诈者

参考例句：

• The fangs of pit vipers are long, hollow tubes. 颊窝毒蛇的毒牙是长的空心管子。 来自辞典例句
• Vipers are distinguishable from other snakes by their markings. 根据蛇身上的斑纹就能把┹蛇同其他蛇类区别开来。 来自辞典例句

13 adder   

n.蝰蛇；小毒蛇

参考例句：

• The adder is Britain's only venomous snake.蝰蛇是英国唯一的一种毒蛇。
• An adder attacked my father.一条小毒蛇攻击了我父亲。

14 primitive   

adj.原始的；简单的；n.原(始)人，原始事物

参考例句：

• It is a primitive instinct to flee a place of danger.逃离危险的地方是一种原始本能。
• His book describes the march of the civilization of a primitive society.他的著作描述了一个原始社会的开化过程。

15 viperine   

adj.毒蛇的，似毒蛇的

参考例句：

• One of the serious complications of viperine bite is renal failure. 肾衰竭是毒蛇咬伤的一种严重并发症。 来自互联网
• That woman has the most viperine tongue! 那个女人有最恶毒的舌头！ 来自互联网

16 immediate   

adj.立即的；直接的，最接近的；紧靠的

参考例句：

• His immediate neighbours felt it their duty to call.他的近邻认为他们有责任去拜访。
• We declared ourselves for the immediate convocation of the meeting.我们主张立即召开这个会议。

17 concoct   

v.调合，制造

参考例句：

• I gave her a tip on how to concoct a new kind of soup.我教她配制一种新汤的诀窍。
• I began to concoct explanations of my own.我开始思考自己的解释。

18 potency   

n. 效力，潜能

参考例句：

• Alcohol increases the drug's potency.酒精能增加这种毒品的效力。
• Sunscreen can lose its potency if left over winter in the bathroom cabinet.如果把防晒霜在盥洗室的壁橱里放一个冬天，就有可能失效。