It gets there when you eat, it comes from you blood and from chemical reactions in your body.

只要你吃东西，就会有屁, 屁在血液中和体内的化学作用产生。

This is a result of melanin in the dead skin cells reacting with oxygen creating a black color —it's not dirt.

这死皮细胞中的黑色素和氧起化学作用生成黑色点点的结果——东西。

Understanding this chemical action forms the basis of drug development and testing today.

理解这种化学作用构成了当今药物研发与测试的基础。

I can't. It's like this chemical thing, you know?

我说出来这像一种化学作用？

Corrode is a verb that usually describes destroying a metal by oxidation or by some other kind of chemical action.

“腐蚀”一个动词，通常用来描述金属因氧化或其他化学作用而遭受破坏的过程。

And a big environmental change was also underway in the last half of the Eocene, thanks to the chemistry of mountain-building.

而在始新世的后半期，山运动的化学作用，也发生了一场巨大的环境变化。

So it’s not just the snack you desire, but the smell itself is a perfect example of chemistry at work, stimulating your brain and body.

因此，这仅仅您想要的零食，而且气味本身就化学作用的完美例子， 可以刺激您的大脑和身体。

Like, how a queen ant's nutrition and pheromones can chemically alter an ant embryo to either produce a soldier or worker ant based on what's needed for the colony.

比如，蚁后的营养和信息素如何通过化学作用改变蚂蚁胚胎，使其根据蚁群的需要产生兵蚁或工蚁。

A yearlong study of more than 400 Alzheimer's patients showed that two drugs that work differently on the brain's chemistry act well together to help slow down the disease.

一项对 400 多名阿尔茨海默病患者进行的为期一年的研究表明，两种对大脑化学作用同的药物可以很好地协同作用，帮助减缓疾病的发展。

They also said that findings from animal cases suggest that their addiction-like behaviors happened only when they had intermittent access to sugar, believing those behaviors to come from the intermittent access, not the actual neurochemical effects of sugar.

他们还表示， 动物案例的发现表明， 只有当它们间歇性地获取糖时， 才会发生类似成瘾的行为，他们相信这些行为来自间歇性的获取，而糖的实际神经化学作用。