新概念第四冊(cè)課文精講 Lesson20:蛇毒
課文20 蛇毒
312. How it came about that snakes manufactured poison is a mystery.
蛇是怎樣產(chǎn)生毒液的，這是一個(gè)謎。
313. Over the periods their saliva, a mild, digestive juice like our own,
蛇的唾液本來和我們?nèi)说南阂粯尤岷停?jīng)過漫長的時(shí)間，
314. was converted into a poison that defies analysis even today.
演變成了今天仍無法分析清楚的毒液。
315. It was not forced upon them by the survival competition;
毒液不是生存競(jìng)爭(zhēng)強(qiáng)加給它們的，
316. they could have caught and lived on prey without using poison,
它們也可以不用毒液捕捉動(dòng)物而生存，
317. just as the thousands of non-poisonous snakes still do.
就像今天成千上萬的無毒蛇那樣。
318. Poison to a snake is merely a luxury;
毒液對(duì)毒蛇來說只不過是一種舒適生存的優(yōu)越手段，
319. it enables it to get its food with very little effort,
它使蛇不用費(fèi)多大力氣就能捕獲到食物，
320. no more effort than one bite.
輕咬一口即可。
321. And why only snakes?
為什么只有蛇才有毒液呢?
322. Cats, for instance, would be greatly helped;
譬如說，如果貓有毒液，那對(duì)貓會(huì)大有幫助，
323. no running fights with large, fierce rats or tussles with grown rabbits
它就不必再和又大又兇的老鼠邊跑邊博斗了，也不必再和大兔子扭斗了，
324. In fact, it would be an assistance to all carnivores
因此，任何食肉動(dòng)物有了毒液，都能從中獲益。
325. though it would be a two-edged weapon when they fought each other.
不過，當(dāng)它們相互撕打時(shí)，毒液就成了利弊參半的武器，可以殺死對(duì)方，也可以被對(duì)方的毒液殺死。
326. But, of the vertebrates, unpredictable Nature selected only snakes (and one lizard).
然而，在脊椎動(dòng)物中，大自然神秘模測(cè)地只選擇了蛇(還有一種蜥蜴)，
327. One wonders saliva into why Nature, with respect from that of others, as other on the blood.
人們弄不清楚大自然為什么在某些蛇的身上調(diào)制出如此高效的毒液來。
328. In the conversion of saliva into poison, one might suppose that a fixed process took place.
人們可能認(rèn)為，唾液轉(zhuǎn)變成毒液，其中有固定的程序。
329. It did not;
其實(shí)沒有。
330. some snakes manufacture a poison different in every respect from that of others,
有些蛇產(chǎn)生的毒液也在各方面與另外一些毒蛇產(chǎn)生的毒液不同，
331. as different as arsenic is from strychnine,
就像砒霜不同于馬錢子堿一樣。
332. and having different effects.
不同毒蛇產(chǎn)生的毒液產(chǎn)生的效果不同，
333. One poison acts on the nerves, the other on the blood.
一種毒液作用于神經(jīng)，另一種毒液作用于血液。
334. The makers of the nerve poison include the mambas and the cobras
產(chǎn)生神經(jīng)毒液的蛇有一種非洲樹眼鏡蛇和眼鏡蛇，
335. and their venom is called neurotoxic.
它們的毒液稱為神經(jīng)毒素。
336. Vipers (adders) and rattlesnakes manufacture the blood poison,
蝰蛇(蝮蛇)和響尾蛇產(chǎn)生血液毒素，
337. which is known as haemolytic.
稱為溶血性毒液。
338. Both poisons are unpleasant,
這兩種毒液都很可怕，
339. but by far the more unpleasant is the blood poison.
但溶血性毒液尤其厲害。
340. It is said that the nerve poison is the more primitive of the two,
據(jù)說，神經(jīng)毒液在兩種毒液中是較為原始的一種，
341. that the blood poison is, so to speak, a newer product from an improved formula.
而溶血性毒液，打個(gè)比方說，是根據(jù)改良配方生產(chǎn)的一種較新的產(chǎn)品。
342. Be that as it may, the nerve poison does its business with man far more quickly than the blood poison.
不過，神經(jīng)毒辣液比溶血性毒液在人身上起作用快得多。
343. This, however, means nothing.
但是，這沒有什么關(guān)系，
344. Snakes did not acquire their poison for use against man
因?yàn)樯哂卸疽翰皇怯脕韺?duì)付人的，
345. but for use against prey such as rats and mice,
而是對(duì)付它的獵物，諸如鼠類，
346. and the effects on these of viperine poison is almost immediate.
毒液對(duì)這些獵物會(huì)立刻起作用。
