# 第四册 Lesson 20 Snake poison 蛇毒

## 一、课文原文

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 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 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.

## 二、重点词汇详解

| 单词 | 音标 | 词性 | 释义 | 用法说明 |
|------|------|------|------|----------|
| manufacture | /ˌmænjuˈfæktʃə/ | v. | 制造，生产 | manufactured poison 制造毒液 |
| saliva | /səˈlaɪvə/ | n. | 唾液 | digestive saliva 消化性唾液 |
| defy | /dɪˈfaɪ/ | v. | 使不可能，违抗 | defies analysis 无法分析 |
| prey | /preɪ/ | n. | 猎物，被捕食者 | live on prey 以猎物为食 |
| luxury | /ˈlʌkʃəri/ | n. | 奢侈，奢侈品 | merely a luxury 不过是奢侈品 |
| tussle | /ˈtʌsl/ | n./v. | 扭打，争斗 | tussles with grown rabbits 与成年兔子扭打 |
| carnivore | /ˈkɑːnɪvɔː/ | n. | 食肉动物 | herbivore 食草动物 |
| vertebrate | /ˈvɜːtɪbrət/ | n./adj. | 脊椎动物 | of the vertebrates 在脊椎动物中 |
| concoct | /kənˈkɒkt/ | v. | 调制，炮制 | concocted poison 调制毒液 |
| potency | /ˈpəʊtnsi/ | n. | 效力，威力 | extreme potency 极强效力 |
| arsenic | /ˈɑːsnɪk/ | n. | 砒霜，砷 | 剧毒物质 |
| strychnine | /ˈstrɪkniːn/ | n. | 马钱子碱 | 剧毒生物碱 |
| neurotoxic | /ˌnjʊərəʊˈtɒksɪk/ | adj. | 神经毒性的 | nerve poison = neurotoxic |
| haemolytic | /ˌhiːməˈlɪtɪk/ | adj. | 溶血性的 | blood poison = haemolytic |
| mamba | /ˈmæmbə/ | n. | 曼巴蛇 | 非洲剧毒蛇 |
| cobra | /ˈkəʊbrə/ | n. | 眼镜蛇 | 亚洲/非洲毒蛇 |
| viper | /ˈvaɪpə/ | n. | 蝰蛇 | adder 欧洲蝰蛇 |
| rattlesnake | /ˈrætlsneɪk/ | n. | 响尾蛇 | 美洲毒蛇 |
| primitive | /ˈprɪmɪtɪv/ | adj. | 原始的 | the more primitive of the two 两者中更原始的 |
| viperine | /ˈvɪpəraɪn/ | adj. | 蝰蛇的 | viperine poison 蝰蛇毒 |

## 三、语法知识点

### 1. How it came about that... ...是如何发生的

> **How it came about that** snakes manufactured poison is a mystery.

- how引导主语从句
- it came about = it happened/occurred
- it是形式主语，that从句是真正主语

### 2. could have done 虚拟过去

> They **could have caught** and lived on prey without using poison...

- could have done = 本可以（但实际没有）
- 表示对过去事实的虚拟假设

### 3. no more...than... 与...一样不...

> ...**no more effort than** one bite.

- no more than = 仅仅，只是
- 此处= only one bite's worth of effort

### 4. Be that as it may 无论如何

> **Be that as it may**, the nerve poison does its business with man far more quickly...

- = nevertheless, regardless
- 固定表达，让步状语
- 虚拟语气的固定用法

## 四、重点句型分析

### 1. come about 发生，产生

> How it **came about that** snakes manufactured poison is a mystery.

- = happen, occur
- 仿写：How did it come about that he left so suddenly?

### 2. live on 以...为食

> ...they could have caught and **lived on** prey without using poison...

- = feed on, subsist on
- 仿写：The islanders live on fish and rice.

### 3. act on 对...起作用

> One poison **acts on** the nerves, the other **on** the blood.

- = have an effect on
- 仿写：This medicine acts on the heart.

### 4. by far 大大地，...得多

> ...**by far** the more unpleasant is the blood poison.

- by far + 比较级/最高级，强调程度
- 仿写：She is by far the best student in the class.

## 五、课文翻译

蛇是如何产生毒液的至今仍是个谜。经过漫长的时期，它们的唾液——一种像我们的一样温和的消化液——被转化成了至今仍无法分析的毒液。这并不是生存竞争强加给它们的；它们本来不用毒液也能捕获猎物为食，就像数千种无毒蛇仍在做的那样。毒液对蛇来说不过是一种奢侈品；它使蛇能以极少的力气获得食物，只需咬一口的力气。而且为什么只有蛇有呢？猫，例如，如果有毒液会大有帮助；不必与大凶鼠追逐搏斗或与成年兔子扭打——只需一口就不再需要费力了。实际上，毒液对所有食肉动物都会有帮助，尽管当它们互相搏斗时会成为一把双刃剑。但是，在脊椎动物中，不可预测的大自然只选择了蛇（和一种蜥蜴）。人们也好奇，大自然为什么对某些蛇调制了效力极强的毒液。

在唾液转化为毒液的过程中，人们可能以为存在一个固定的过程。事实并非如此；有些蛇制造的毒液与其他蛇的毒液在每个方面都不同，就像砒霜与马钱子碱一样不同，效果也不同。一种毒液作用于神经，另一种作用于血液。制造神经毒液的包括曼巴蛇和眼镜蛇，它们的毒液被称为神经毒素。蝰蛇和响尾蛇制造血液毒液，被称为溶血毒素。两种毒液都不令人愉快，但更令人不快的是溶血毒素。据说神经毒素是两者中更原始的，溶血毒素可以说是改良配方的新产品。无论如何，神经毒素对人的作用比溶血毒素快得多。然而这并不意味着什么。蛇获得毒液不是为了对付人，而是为了对付老鼠等猎物，而蝰蛇毒液对这些猎物的作用几乎是即时的。

## 六、语言点精讲

### 1. 写作手法：追问式论证

- 连续追问：为什么蛇有毒液？为什么只有蛇？为什么有些毒液如此猛烈？
- 以科学分类（神经毒素vs溶血毒素）回答部分问题
- 开篇以mystery起，结尾回归实用主义（毒液是对付猎物的）

### 2. 文化背景

- **蛇毒研究**：现代蛇毒研究已能分离各种毒素成分，用于开发抗蛇毒血清和药物
- **神经毒素（neurotoxin）**：作用于神经系统，如眼镜蛇毒素
- **溶血毒素（haemolytic toxin）**：破坏红细胞和血管壁，如蝰蛇毒素

### 3. 修辞分析

- **设问**：And why only snakes?——用反问推进论证
- **类比**：as different as arsenic is from strychnine——用已知类比未知
- **拟人**：unpredictable Nature, Nature concocted——赋予自然意志

## 七、课后练习要点

1. **理解题**：What are the two different ways in which snake poison acts?（神经毒素和溶血毒素）
2. **语法题**：could have done 虚拟过去与 can have done 推测过去的区别
3. **词汇题**：区分 neurotoxic/haemolytic/viperine/cobra/mamba 的分类
4. **翻译练习**：Be that as it may 等固定表达的处理

## 八、本课小结

本课探讨**蛇毒的起源与分类**，核心内容：蛇毒由唾液进化而来，分为神经毒素（眼镜蛇等）和溶血毒素（蝰蛇等），后者更痛苦但前者对人类作用更快。语法重点包括how引导主语从句、could have done虚拟过去、no more...than比较、Be that as it may让步表达。写作手法上运用追问式论证和科学分类，兼具好奇心和知识性。