Watch videos with subtitles in your language, upload your videos, create your own subtitles! Click here to learn more on "how to Dotsub"

The Cell - The Hidden Kingdom (Part 5/6)

0 (0 Likes / 0 Dislikes)
The two Germans believed that new cells formed spontaneously and grew up like crystals from a tiny spec of nucleus material. They claim to have seen this under the microscope - it was almost as if new cells had come out of nowhere. Now, if you're thinking this sounds familiar from earlier in the story, you're absolutely spot on. You see, this idea of cell formation, was uncannily similar to the theory of spontaneous generation. By this time biologists had dismissed the idea that larger animals could spring out of inanimate matter, but could it happen with new cells, and new microbes? Spontaneous generation seemed to be the medieval idea that would never die.

Paris, 1860 The French version of the Royal Society announced a competition to settle the question of spontaneous generation once and for all. They had an agenda. They knew this theory was holding up the advance of biology. The award, a cool two and a half thousand Francs. One young French scientist was determined to win the prize. You probably come across his name pretty much every day without even realising it. Louis Pasteur is much better known for his work sterilising milk - we call it pasteurisation. But in the 1860's he was a young scientist struggling for credibility and probably short of a Franc 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 encouraged 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 teeming with microbes. Life, they claimed, had spontaneously generated.

Pasteur 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? Pasteur knew that he had to deign a new type of flask that let in air, but at the same time, kept out the surrounding dust and microbes, a seemingly impossible challenge.

What sort of temperature is that? That looks hot! 2,000 degrees. How many?! 2,000 …. 2,000 degrees? That's amazing! As simple as that? That is amazing …. that's really skilfull. 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 is we fill it. Well, 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 spontaneaous 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, Pasteur set up 2 flasks, one with a swan neck and one with a neck open to dust particles. Now, we recreated the experiment a couple of weeks ago. Here are the 2 flasks with the broth in them This one is Pasteur's, with the swan neck and you can see that the broth is perfectly clear. This one is 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." Pasteur made a tidy sum. He'd shown that new microbes must have drifted in on the breeze and he'd sounded the death knell for spontaneaous generation. It couldn't account for new mice, new microbes or new cells. So what did?

It seems incredible to me that an idea like spontaneous generation could have lasted as long as it did. By the 19th century the world had changed beyond recognition and those changes were being driven by science and engineering. The industrial revolution was in full swing. People now believed in machines, scientific laws, in cause & effect. So when the next generation of scientists wanted to find out where new cells really came from, they wanted a functional explanation, that didn't rely on cells simply springing forth from inanimate matter. The quest had started, even before Pasteur's killer experiment in Berlin, the birthplace of cell theory. And it was here that two friends had been searching for a new explanation for the origin of cells. Robert Remack was a Polish Jew while his friend Rudolf Bircher was a politically astute German. One man would do all the key research and the other would take all the credit. See if you can work out which is which. Robert Remack is not one of the best known names in the history of science but for me, he's a genuine hero for our story. Remack was Jewish, so attaining the professorship that he deserved, was always going to be an uphill struggle. He was forced to do his research in a dingy attic apartment Despite these obstacles, Remack set out to discover how new cells originated. He realised his best hope was to look in a place where he'd be guaranteed to see lots of cells forming. Professor Redies had helped us to recreate Remack's experiment from the 1840's.

The chick embryo was the animal model of choice for embriology, at the time because eggs are very easy to get, they were very inexpensive and also the embryo is accessible. That means you can now take some scissors and cut a hole here on top. Oh, and there it is. The embryo floats on top. Ok. We're going to cut a blood vessel now and collect a little bit of blood. So, I have a glass pipette here, and I'm going to suck a drop of blood. Now, here you can actually see that there is red fluid in the pipette. It contains blood cells, red blood cells and I'm putting them on a glass here. And to see them better we put a cover slip on top, so that we can look at it under the microscope. Here we go …. now let's have a look. We take the microscope here, which is of the type that Remack may have used. It's a really old one. I have to adjust the light source with the mirror here. It's not the type of scope that you're used to using? Well, the scopes we're using are a bit more modern now. You can actually look with both eyes. I will have to close one eye and look through here. And what you can see, actually, is many, many blood cells. They are still floating around a little bit, because the fluid is moving. They are round, most of them, but occasionally I see a cell in division, which is not round, but which has a men .... the … it is … I don't know the technical term in English. There is some invagination of the cell membrane. That is he same word, invagination. So it begins ...

Video Details

Duration: 10 minutes and 20 seconds
Country: United Kingdom
Language: English
Producer: BBC Four
Views: 2,272
Posted by: vallisso on Oct 28, 2009

Episode 1 of 3

Dr Adam Rutherford introduces a new three-part series that tells the extraordinary story of the scientific quest to discover the secrets of the cell and of life itself. Every living thing is made of cells, microscopic building blocks of almost unimaginable power and complexity.

The first part explores how centuries of scientific and religious dogma were overturned by the earliest discoveries of the existence of cells, and how scientists came to realise that there was, literally, more to life than meets the eye.

Caption and Translate

    Sign In/Register for Dotsub to translate this video.