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 competition; 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 5 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 also why Nature, with some snakes, concocted poison of such extreme potency.

In the conversion of saliva into poison, one might suppose that a fixed process took place. It did not; some snakes manufactured 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 15 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

conversion (1.10) $/\mathrm{k}$ ən’vɜːʃən/ n. 转变

arsenic (l.11)/’ɑːsnɪk/n. 砒霜

strychnine (1.12) / ’strɪkniːn/ n. 马钱子碱

mamba (1.13) /’mæmbə $/n$ . 树眼镜蛇

cobra (1.13) $/\prime \mathrm{k}\partial \sigma \mathrm\partial /n$ . 眼镜蛇

venom (1.13) /’venəm/ $n$ . 毒液

neurotoxic (1.13)/, njʊərəʊ'tɒksɪk/adj. 毒害神经的

viper (1.14)/varpo/ $n$ . 虫奎蛇

adder (1.14) $/2 \approx d \ni /n$ . 蝮蛇

rattlesnake (1.14) /’rætlsneɪk/ n. 响尾蛇

haemolytic (1.14) /|hiːməʊ'lɪtɪk/adj. 溶血性的

viperine (1.19) /'vaɪpəraɪn/adj. 毒蛇的

saliva (1.1)/sә'larvә/n. 唾液

digestive (1.2) /daɪ'dʒestɪv/adj. 助消化的

defy $\left( {1.2}\right) /{\mathrm{d}}_{\mathrm{I}}$ 'faɪ/v. 使不可能

analysis (1.2) $/{\theta }^{\prime }n$ æləsɪs $/n$ . 分析

prey (1.3) /preɪ/ $n$ . 被捕食的动物

fierce (1.6)/fIgs/ adj. 凶猛的

tussle (1.6) $/\prime \mathrm{t}\Lambda \mathrm{s}\partial /\prime n$ . 扭打

carnivore (1.7) $/$ ’kaːnrvɔː/ $n$ . 食肉动物

vertebrate (1.8) $/$ ’ $\mathrm{v}3$ ːtɪbɪɪt/ $n$ . 脊椎动物

lizard (1.9) / ’lizəd/ n. 蜥蜴

concoct (1.9) $/k$ an’kɒkt/v. 调制

potency (1.10) $/$ ’pəʊtənsi/ n. 效力 Unit 3 Lesson 20

An Indian grass snake swallowing a frog

Notes on the text 课文注释

1 How it came about that snakes ... a mystery.

这句话的主语是一个句子: How it came about that snakes manufactured poison, 谓语部分是 is a mystery。主语从句中的 it 是形式主语, 真正主语是 that snakes manufactured poison, 因为主语太长, 所以使用 it 作先行主语的结构。

2 over the periods, 经过很长时间。

3 live on, 靠 …… 生活。

a two-edged weapon, 一把双刃刀, 这里的意思是: 如果食肉动物都有毒液, 就会造成食肉动物之间的互相残杀。 5 act on, 对 …… 起作用。

by far the more unpleasant, 更难受得多, by far 是 “ …… 得多” 的意思。

7 so to speak, 插入语, 有 “可以这样说”, “打个比方说” 的意思。

8 Be that as it may, 这是一个倒装的让步状语从句, 相当于 however that may be, 可译成 “尽管如此”。

9 does its business with man, 在人的身上发挥作用, 要人的命。

10 the effects on these of viperine poison, these 是指 rats and mice, 介词宾语结构 of viperine poison 是作 effects 的定语。

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, 它能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搏斗了,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器,可以杀死对方,也 Unit 3 Lesson 20 可以被对方的毒液杀死。然而, 在脊椎动物中, 大自然神秘莫测地只选择了蛇 (还有一种蜥蜴), 人们还弄不清大自然为什么在某些蛇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。有些蛇产生的毒液在各方面与另外一些毒蛇产生的毒液不相同,就像砒霜不同于马钱子碱一样。不同毒蛇的毒液产生的效果也不同,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出的一种较新的产品。不过, 神经毒液比溶血性毒液在人身上起作用快得多。但是,这没什么关系,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。

Comprehension 理解

Answer these questions:

1 Why does the author find it odd that snakes should be capable of manufacturing poison?

2 What is the difference between neurotoxic and haemolytic poison?

Vocabulary 词汇

Refer to the text to see how the following words have been used, then write sentences of your own using these words: mild (1.1); converted (1.2); defies analysis (1.2); the survival competition (1.3); carnivore (1.7); a two-edged weapon (II.7-8); concocted (I.9); extreme potency (I.9); viperine (I.19).

The paragraph 段落

A Drawing your information from the first paragraph (lines 1-9), write a list of points in note form to answer the following question: Why is the author justified in stating that Nature behaved in an unpredictable way in allowing snakes to manufacture poison?

B Read the last paragraph again (lines 13-19). Then, using the list of points given below, reconstruct the paragraph in your own words as far as possible. Do not refer to the passage until you have finished the exercise.

1 Nerve poison (e.g. mambas): neurotoxic.

2 Blood poison (e.g. vipers): haemolytic.

3 Blood poison the more unpleasant.

4 Nerve poison possibly the more primitive.

5 Blood poison a later development.

6 But nerve poison acts more quickly on man.

7 Purpose of poison: not against man, but snake's prey: e.g. rats.

C Write a paragraph of about 200 words on one of the following subjects:

1 Our fear of snakes.

2 The survival competition.

Unit 3 Lesson 20

Key structures 关键句型

A Compare these two sentences:

Instead of saying: They had the ability to catch and live on prey without using poison if they wanted to (but they didn't).

We can say: They could have caught and lived on prey without using poison. (1.3)

Write sentences using the following expressions:

could have succeeded; could have stayed; could have bought. B Write sentences using the following expressions:

force upon (II.2-3); live on (I.3); conversion into (1.10); different from (1.11); act on (1.12); effect on (1.19).

C Compare these two sentences:

Instead of saying: They could have caught and lived on prey without using poison, just as the thousands of nonpoisonous snakes still catch and live on prey without using poison.

We can say: They could have caught and lived on prey without using poison, just as the thousands of nonpoisonous snakes still do. (II.3-4)

Complete the following sentences by adding the correct form of ${do}$ :

1 Even though he has retired, he still gets up early just as he always _____.

2 He certainly enjoys music as much as you _____.

3 If you act as he _____ you won't be very popular.

D Study the following sentence:

Both poisons are unpleasant, but by far the more unpleasant is the blood poison. (II.14-15) Why is the more used here and not the most? Write two sentences using the more and the most.

E Note how the word far has been added for emphasis in this sentence: Nerve poison does its business...far more quickly than ... (1.17)

The word much may be used in the same way. We can say much more quickly, using much in an emphatic way.

Write sentences using the following phrases: much more expensive; far more difficult; far less exciting; much less interesting.

Special difficulties 难点

A Study the following pairs of words and then write sentences of your own to bring out the difference.

1 merely (1.4) - only

I'm not blaming you. I'm merely trying to find out how this happened.

Only the head of the department can authorize a withdrawal from a course.

2 fierce (1.6) - furious

You can see armed guards along the border accompanied by fierce dogs.

He was terribly annoyed. Indeed, he was furious! Unit 3 Lesson 20

3 take place (l.10) - take part

All these events took place before you were born.

How many of you are taking part in the play?

4 prey (I.3) - pray

The tiger seized its prey and tore it into pieces.

You've done your best. All you can do now is pray for success.

B Explain the verbs in italics in the following:

1 How it came about that snakes manufacture poison is a mystery. (I.1)

2 I'm sorry I said that. I don't know what came over me.

3 He came up with some very interesting ideas.

4 I came across an old friend of yours while I was abroad.

C Write sentences using the following words and phrases: enable (I.4); running fights (I.6); in fact (I.7); in every respect (1.11); so to speak (1.16); be that as it may (ll.16-17).

D Supply full stops and commas where necessary in the following paragraph. Do not refer to the passage until you have finished the exercise:

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 hacmolytic 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. (ll.13-19)

Multiple choice questions 多项选择题

Choose the correct answers to the following questions.

Comprehension 理解

1 One of these statements is true. Which one?

(a) Snakes need poison to digest their food.

(b) Snakes can feed on other animals without the use of poison.

(c) Non-poisonous snakes find survival more difficult than poisonous ones.

(d) All snakes are capable of manufacturing poison.

2 The possession of poison in the saliva makes hunting _____

(a) easy for all carnivores

(b) a two-edged weapon when carnivores fight each other

(c) almost effortless for snakes

(d) unpredictable, as Nature intended

Unit 3 Lesson 20

3 The poison that acts on the blood _____.

(a) acts less rapidly than nerve poison

(b) doesn't affect the victim as badly as nerve poison

(c) is made by snakes like mambas and cobras

(d) was probably the first of the two kinds of poison to be developed

4 Human beings _____.

(a) can't compare with prey such as rats and mice

(b) respond to all snake poisons in the same way

(c) are likely to survive nerve poison but not blood poison

(d) are not the intended victims of snake poison

Structure 句型

5 They _____ have been able to catch and live on prey without using poison. (1.3)

(a) might (b) should (c) would (d) must

6 They could have caught and lived on prey without _____ poison. (1.3)

(a) to use (b) use (c) the use of (d) have used

7 For _____ snakes, poison is merely a luxury. (1.4)

(a) these (b) a (c) - (d) an

8 Blood poison is the more unpleasant _____ . (1.15)

(a) of them all (b) of the two (c) in the world (d) among them both

Vocabulary 词汇

9 Saliva is a natural _____ . (ll.1-2)

(a) oil in the body (b) snake-poison (c) digestive process (d) body fluid

10 Poison would be _____ to all carnivores. (1.7)

(a) an asset (b) a help (c) a necessity (d) a disadvantage

11 Arsenic and strychnine _____ us in different ways. (I.11.11-12)

(a) effect (b) result (c) affect (d) cause

12 The nerve poison is thought to be _____(ll.15-16)

(a) less highly developed (b) more potent

(c) more recent (d) less complicated