师：同学们好，这节课我们学习科学探究的基本过程。学完这节课，大家要能说出科学探究的一般过程，并尝试运用科学探究的方法，体验其一般过程。什么是科学探究呢？牛顿看到掉落的苹果，发现了万有引力；普利斯特利在实验室得出植物可以更新空气；弗莱明偶然发现青霉素有强大的杀菌作用。他们是经过无数次思考、探索、实验，才得出这些结论的。面对问题，他们形成了一定的思维方式和解决办法，像他们那样思考和解决问题的方法，就是科学探究。

　　科学家到底是怎样进行科学探究的呢？今天我们以巴斯德的鹅颈瓶实验为例，分析科学探究的基本过程。巴斯德可是科学界的牛人，出生在法国，毕业于巴黎大学，在很多领域都有突出贡献，尤其在微生物学和化学方面。在微生物学上，他弄清了发酵的奥秘，创立了巴氏灭菌法。我们喝的鲜牛奶盒上常常能看到“巴氏消毒”这几个字，这种消毒法既能杀灭细菌，又不会影响牛奶的口感，被广泛运用。在免疫学上，他征服了狂犬病、鸡霍乱，成功研制出炭疽病减毒活性疫苗，使当时的畜牧业免受灭顶之灾。学术上，他创立了微生物生理学，还否定了微生物自然发生说。当时的人们受宗教影响，大多认同生命起源的自然发生说，即蛆是由腐肉产生的，细菌是肉汤里面生出来的。巴斯德的鹅颈瓶实验打破了这一禁锢人们大脑的学说，形成了生生说理论，也就是生物是由生物自己产生的。那什么是鹅颈瓶实验？鹅颈瓶长什么样子呢？可能大家脑中有一堆问题。后来有人模拟当时的情境做了这个实验，我们一起来看看实验经过。

　　For his work sterilizing milk. We call it pasteurization. But in the 18, he was a young scientist struggling for credibility. And probably short of a Frank or two, he was convinced that spontaneous generation was a load of medieval bunkum. Pasteur set out to disprove the idea and win the competition.

　　Spontaneous generation was a hot topic. Researchers had spent years studying microbes in the laboratory, or rather inside glass flasks. They'd fill a flask with nutrient broth, a mixture of sugars and foods that encourage growth but was itself sterile, devoid of life. And then they waited to see what happened. It all turned into a bizarre battle of the flasks. Now, the spontaneous generation crowd believed that as long as there was a nice airflow to get things going, that life would suddenly spring out of nowhere. And lo and behold, after a couple of weeks, the solution went cloudy. And when they looked at it under the microscope, it was teaming with microbes. Life they claimed had spontaneously generated. Pastor didn't buy it. He suspected that the microbes came in from the outside on dust particles and set up home in the flask. And as they multiplied, the flask went cloudy. But how to prove it? Paster knew he had to design a new type of flask that let air in, but at the same time kept out the surrounding dust and microbes, a seemingly impossible challenge.

　　That is amazing. That's really skillful. And then we wait for it to cool. And I'll cut that off there and gently flame the end so that it's not sharp. And the next stage will be to fill it. I'm really impressed with that. Well done, Ray. That was amazing. Thank you.

　　This was Pasteur's ingenious solution, a swan neck. Now, it may not look like much, but this simple design changed the course of science. Have a look. The air can get in through here, but the microbes get stuck in the bottom of the curve. So the broth inside should remain sterile and clear and free of microbes. Yet the spontaneous generation folk were still convinced that even with the swan neck, new life would form of its own accord. Who was right? To find out, Pastor set up two flasks, one with the swan neck and one with the neck open to dust particles. Now, we recreated the experiment a couple of weeks ago. Here are the two flasks with the broth in them. This one is pastor's with the swan neck, and you can see that the broth is perfectly clear. This one's the open neck flask, which is very cloudy, full of bacteria. Pasteur had won the competition, and he proudly declared, never again will the doctrine of spontaneous generation recover from the mortal blow struck by this simple experiment.