Snake Poison
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 than one bite. And why only snakes? Cats, for instance, would be greatly helped; no running with large, fierce rats or tussles with grown rabbits - just a bite an no more effort needed. In fact it would be an assistance to all the carnivorae -- 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.
蛇是如何制造毒药是一个迷。长久以来它们的唾液和我们的类似，无毒，帮助消化唾液，而转化成了至尽难以分析其结构的毒药。而这并不是因为生存竞争强迫而成的，蛇可以和数千种的无毒蛇一样，不依靠毒药捕食而谋生。毒对于蛇来说是一种“奢侈”。毒使得蛇可以花费很小的力气得到事物，仅仅是咬一口而已。为什么只有蛇有毒呢？例如猫如果有毒对于它们会很有帮助。不再需要追逐凶猛的大老鼠或和野兔争斗，只需要咬一口。尽管有些古老，但实际上毒会对所有的食肉动物彼此争斗时有帮助。但是不可遇见的自然只选择了蛇（和一种蜥蜴）。为什么有些蛇能制造出如此剧烈的毒药？
有人认为由唾液转变为毒药经过了一个特定的过程。然而不是的。一些蛇用独特的方式制造毒药。就象砒霜同番木鳖碱的区别一样，并有着不同的作用。一种毒药是作用于神经的，而另一种则是作用于血液的。树眼睛蛇，眼镜蛇和他们的毒液被称为神经性毒液，蝰蛇和响尾蛇则制造血液性毒液，即溶血剂。这两种毒都是令人不快的，但血液性毒液更为惹人讨厌。据说神经性毒液占大部分，而血液性毒液则是经过改良的新品种。但是神经性毒液作用于人体的速度更快。这没有什么意义。蛇的毒液不是抵抗人类的而是用于捕食老鼠等动物的。而蛇毒在这些动物身上的效果几乎是立即的。
