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If you've ever called snakes "poisonous" around a herpetologist or, you know, that friend of yours, you know which one I mean,
如果你当着爬虫学家的面说蛇是“有毒的”，
there's a good chance you'll receive a lecture about the difference between venoms and poisons.
那么他很可能会给你上一堂课告诉你毒液和毒物之间的区别。
And it's true that most snakes aren't considered poisonous. But nature loves an exception. Meet the tiger keelback.
确实大部分蛇都不被认为是有毒的。但是大自然喜欢例外。来见见赤练蛇。
They've got the best of both worlds: poison for their predators and venom for their prey.
它们很好地诠释了这两个词：于敌人，是毒物；对猎物，是毒液。
It can be easy to confuse the terms venom and poison, but the difference does actually matter.
毒液和毒物很容易弄混淆，但是它们之间的区别很重要。
Both are made up of toxins, biological chemicals that mess with body functions in small amounts.
两种都是由毒素组成， 毒素是小剂量干扰身体功能的生物化学物质。
The technical difference has to do with how they get into a victim's body.
它们在技术上的差异和它们进入受害者身体的方式有关。
Poisons enter passively, by being eaten, breathed in, or absorbed through the skin.
毒物是被动地通过咬、吸入或是通过皮肤吸收进入。
And because of that, they're usually defensive, an organism's way of saying "Hey! Don't touch me! You will regret that!"
因此，它们通常是防御性的，是有机生物表达‘喂！别碰我！你会后悔的！’的一种方式。
Venoms, on the other hand, are actively injected into the body, like, via a pair of pointy snake fangs, for example.
另一方面，毒液是主动注射进体内的，比如通过蛇的那一对尖尖的毒牙。
Venom can certainly be used defensively, but often, venomous animals are predators that use their toxins offensively,
毒液绝对可以是防御性的，但是通常带有毒液的动物都是捕食者，会攻击性的使用它们的毒素
so they can enjoy a meal without all that troublesome struggle.
以轻松美餐一顿。
Since venoms and poisons tend to be used differently, they usually contain different kinds of toxins.
由于毒液和毒物使用不同，它们通常包含不同的毒素。
So a doctor would want to treat a snake poisoning differently than a snake bite, or what's known as envenoming.
所以医生治疗蛇中毒和蛇咬伤（蛇咬中毒）的方法不同。
And the distinction is particularly important if the snake in question is a tiger keelback.
并且，如果问题中的蛇是赤练蛇的话，差别就尤为重要。
These snakes can be found across Southeastern Asia, and they belong to a huge and diverse family of snakes called the Colubridae.
这类蛇出没于东南亚，它们属于一种巨大且种类繁多的蛇科—游蛇科。
These are sometimes referred to as "rear-fanged" snakes because unlike rattlesnakes or cobras,
有时这些被称为后毒牙蛇，因为和响尾蛇或眼镜蛇不同，
which pump venom forcefully through hollow fangs in the front of their mouths,
响尾蛇或眼镜蛇通过前牙激烈地喷射毒液，
colubrid fangs sit further back in the jaw and deliver venom along open grooves.
无毒尖牙在下颚后位，并顺着开口凹槽传送毒液。
And they have to kind of chew on their prey a bit to get the venom moving.
并且它们需要一点点咀嚼猎物才能让毒液传送。
Most of the time, tiger keelbacks use their venom to take down tasty fish, tadpoles, and their favorite: frogs and toads.
大部分时候，赤练蛇利用它们的毒液拿下美味的鱼类以及它们最爱的青蛙和蟾蜍。
They rarely bite humans, but when they do, it's not a fantastic experience for the human.
它们很少咬人类，但是当它们这么做时，对人类而言可不是一场美妙的体验。
The venom can cause hemorrhaging and mess with blood clotting,
毒液可以造成大出血以及扰乱血液凝结
leading to excessive internal and external bleeding, and in several known cases, death.
导致大量内外出血，还有几个造成死亡的案例。
Thankfully, antivenom is usually an effective treatment, if delivered in time.
还好，如果运送及时，抗蛇毒素通常是一种有效的治疗方法。
Now, all this talk of killer snake bites might sound scary, but it's important to remember that snakes don't want to bite you!
被蛇咬伤听起来可能很恐怖，但是重要的是要记住，蛇并不想咬你！
Really, they don't! They'd much rather save their venom for their prey.
真的不想！它们更愿意把毒液留给它们的猎物。
They don't want to waste it on something they can't eat.
它们不想把它浪费在一些不能吃的东西上。
And that may be partly why the tiger keelback usually fends off threats another way.
这或许是因为赤练蛇经常以另一种方法躲避威胁。
On the back of these snakes' necks are several pairs of nuchal glands.
在这些蛇脖子背面是几对颈背腺体。
If the right pressure is applied, these glands crack open and spew out a stinky, toxic yellow-ish pus.
如果施加的压力适当，这些腺体会泵开并喷出臭臭的有毒微黄脓汁。
The poisonous nature of this stuff was first noted in 1935,
这种物质的有毒性质首次发现于1935年，
when a scientist who was dissecting a keelback cut into its nuchal glands, accidentally spraying the poison right into his eye!
当时一名解剖赤练蛇的科学家切开了其颈背腺体，意外将这种毒素喷射进了他的眼睛！
Which is just one of the many stories that science teachers have heard, and why they get so fussy about you wearing your safety goggles.
这只是科学课老师们听过的众多故事之一，也是他们让你戴上防护眼镜的原因。
The poison contains bufadienolides, which can cause acute pain and temporary damage to the cornea if they get in your eyes.
这种毒素中含有蟾蜍二烯羟酸内酯，如果进入眼睛，会引起剧烈疼痛以及暂时性的角膜损伤。
When ingested or inhaled, they can irritate any tissue they touch and even cause heart problems.
当吞下或吸入它们，它们会刺激任何接触到的组织，甚至会导致心脏问题。
And the snakes know how to use their poison.
蛇知道如何使用它们的毒素。
When confronted with danger, they assume an arched posture and aim their neck towards the threat.
面对危险时，它们会摆出拱形姿势并以脖子为目标应对威胁。
Sometimes, they'll even swing their neck at an attacker, poison glands first, in a maneuver that scientists have delightfully named a "neck butt."
有时，它们甚至会冲着袭击者扭转脖子，首先给腺体投毒，科学家将这种演练戏称为“neck butt”。
Maybe the most interesting thing about this poison is that they don't make it. They pick it up from the toads they eat.
或许关于这种毒素最有趣的是它们不制造这种毒素，而是从吃掉的蟾蜍身上获取。
Research has shown that tiger keelbacks living on toad-free islands don't have these poisons, but they can become poisonous if given toxic toads.
研究表明生活在没有蟾蜍的岛屿上的赤练蛇没有这种毒素，但是如果给它们有毒的蟾蜍，它们就会变成有毒的。
And you'd think that a lack of poison would be a problem for a newborn snake,
你会认为缺乏毒素对刚出生的小蛇是一个问题，
but it turns out mama keelbacks can pass toxins along to their young.
但是事实是蛇妈妈可以将毒素传给它们的下一代。
It's unclear if she adds it to the yolks or just bathes her eggs in the stuff.
蛇妈妈是否会将毒素添加到卵黄或是用这种物质给蛇蛋洗澡就不得而知了。
Experiments have shown that keelback babies absorb toxins through their eggshells.
实验表明赤练蛇宝宝通过蛋壳吸收毒素。
Either way, by the time baby keelbacks hatch, they're ready to defend themselves.
不管怎样，一旦蛇宝宝孵化，它们马上就能够保护自己。
And here's something super weird: the snakes are more likely to flee from threats than face them neck-on if they've been deprived of toads,
有件事超级奇怪：如果缺少蟾蜍作为食物，蛇更有可能逃离而不是面对威胁，
suggesting the animals somehow know when they're poisonous.
这表明有没有毒，动物们知道地明明白白。
Also, the snakes don't just take the toad toxins as-is and stick them in their glands,
同样，蛇并不只是将蟾蜍毒素刺进腺体中，
they actually modify them chemically to make them even more potent.
它们用化学方式对毒素进行修改，让它们变得更加强效。
The tiger keelback is definitely the best-known example of a poisonous snake, but it's likely not the only one.
赤练蛇绝对是有毒蛇类中最知名的一种，但是可能不是唯一的一种。
Other related species have nuchal glands, so they might have poisons of their own that simply haven't been studied.
其他近缘种有颈背腺体，所以它们可能本身含毒素，只是还没进行过研究罢了。
Research has found that other snakes, like garter snakes, can eat so much poisonous prey their organs become toxic to predators.
研究发现其他蛇类，如花纹蛇，可以吃很多有毒猎物，所以它们的器官对捕食者是有毒的。
Since most people don't usually eat snakes, there could be a number of species that would make us sick that we just don't know about.
由于大部分人不经常吃蛇，所以有很多种类都会让我们患病，只是我们不知道而已。
So future studies may reveal that the tiger keelback isn't that much of an exception after all.
所以未来的研究或许能揭露赤练蛇并不是例外。
In the meantime, you can tell that pedantic friend of yours that there definitely are poisonous snakes. So Mleh!
同时，你可以告诉你那个喜欢卖弄学问的朋友，绝对有有毒的蛇。略略略...
Thanks for watching this episode of SciShow! And a special thank you especially to our patrons on Patreon.
感谢收看本期《科学秀》！特别感谢Patreon的赞助人。
We wouldn't be able to have all this fun making awesome educational science videos like this if it weren't for the support of our patron community.
如果没有你们的支持，我们不可能制作出这么有趣的教育性科学视频。
If you'd like to learn more about joining that community, or how you can help us do what we do, you can head on over to Patreon.com/SciShow
如果想知道如何加入我们的社区或是如何帮助我们，请移步Patreon.com/SciShow。
