$课文20 蛇毒

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

蛇是怎样产生毒液的，这是一个谜。

313. Over the periods their saliva, a mild, digestive juice like our own,

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，

314. was converted into a poison that defies analysis even today.

演变成了今天仍无法分析清楚的毒液。

315. It was not forced upon them by the survival competition;

毒液不是生存竞争强加给它们的，

316. they could have caught and lived on prey without using poison,

它们也可以不用毒液捕捉动物而生存，

317. just as the thousands of non-poisonous snakes still do.

就像今天成千上万的无毒蛇那样。

318. Poison to a snake is merely a luxury;

毒液对毒蛇来说只不过是一种舒适生存的优越手段，

319. it enables it to get its food with very little effort,

它使蛇不用费多大力气就能捕获到食物，

320. no more effort than one bite.

轻咬一口即可。

321. And why only snakes?

为什么只有蛇才有毒液呢？

322. Cats, for instance, would be greatly helped;

譬如说，如果猫有毒液，那对猫会大有帮助，

323. no running fights with large, fierce rats or tussles with grown rabbits

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，