All right, so what we want to do now is spend a few minutes talking about some of the early microscopists, because they were really important contributors to our understanding of life that's smaller than what you can see with the naked eye. And there are two individuals I want to highlight. One was named Robert Hooke. Robert Hooke was born in 1635. He died in 1708. He was really an amazing guy. He wasn't just a microscopist, he was actually an astronomer.
He was one of the first to infer the rotation of Jupiter. He worked with Robert Boyle, who was one of the chemists. Boyle's law was one of the gas laws you probably learned about if you took Chem 32 at City College or anywhere else. So he was an astronomer.
He was a chemist. He was a painter. He actually started by interning with a painter, so he was a great artist.
You can actually tell that he's a great artist by looking at his diagram here on the right-hand side of the slide, where he showed, drew what he was seeing under the microscope when he sliced a piece of cork very thinly and looked at it under the microscope. He was a professor of geometry and he published a book called Micrographia, which is considered his seminal work in microscopy, and he Showed all sorts of different things under the microscope, including cork, the microbes in fleas and other insects. He drew soap bubbles that he saw under the microscope. Pretty incredible, pretty incredible individual.
Not a very happy person or pleasant person, apparently. So if you are interested in him sort of as a character, he was quite a character, but very, very brilliant man. brilliant in many different areas of science. Another really important scientist and early microscopist was a gentleman named Anton von Leeuwenhoek.
And Leeuwenhoek lived in Delft. He was a draper. He actually sold cloth. And that was his day job. And then what he did for a hobby was he built the most amazing microscopes.
And so this was his microscope, this little, um, it looks like a, almost like a violin, right? And what he would do is right here where I've got my little mouse cursor, he would put a ball of ground glass. And he was so good at making these little balls of ground glass that he could magnify specimens and look at them under his, using his little microscope. He was able to look at things and they literally look as good as the things we see under our microscope today in our microbiology lab at City College.
So these were, they look rudimentary, but they actually, he was able to get beautiful. beautiful images from these microscopes. And the Royal Society in London would send him all sorts of specimens to look at, and they would commission him to look at things.
So he, and he was also not unsurprisingly a great artist. In fact, this picture here shows some drawings he did of sperm. And he looked at his own sperm under the microscope.
And it's a really funny story. And if you're interested, you can actually, this is the this is a link, but you won't be able to access it for my video. I will put a link up here to this radio lab.
And if you want to listen to the first like three minutes, it's not very long. You can go, you can go click on the link that I'll add to this video and go ahead and listen to it. It's wonderful where they talk about how he looked at his own sperm under the microscope.
Anyway, he was a wonderful microscopist and really got, brought us much further along in our and our ability to see and understand that there was this whole world out there, this whole microbial world out there. All right, so about the time that Hooke and Levenhook were building their beautiful microscopes, there were two competing theories about where life came from. And the one that had been predominating for many years was something called spontaneous generation.
So this is the idea that life just can spontaneously arise because there are vital forces that can sort of infuse themselves into something that's not living and cause it to become the life. And then there were other people who had this hypothesis that no, no, life can only arise from pre-existing life. So this is this idea of biogenesis. And these are these two competing theories. And so, and there was evidence for both theories.
I know you're asking evidence for spontaneous generation. So the next thing I'm going to do is play you a little video and they'll describe in this video, you know, some of the evidence that people felt supported this theory or this idea, hypothesis, spontaneous generation. All right, here we go. Prior to Charles Darwin, scientists had some rather strange ideas concerning how life began.
They believed that living organisms came into being rapidly and spontaneously over a period of just a few weeks. The scientific community believed in spontaneous generation for 2000 years and it is a stark reminder that even a majority of scientists can be wrong. In his classic 17th century description of spontaneous generation, scientist Jan Baptist van Helmond suggested that mice came from dirty underwear.
When you put a piece of sweaty underwear in an open mouth jar together with a piece of wheat, after 21 days the ferment coming out of the underwear changed the wheat into mice. But what is even more amazing, is that the mice are not small or aborted mice, but adult mice emerge. Another evidence offered for spontaneous generation was the rotting meat experiment.
17th century scientists observed that if meat was placed in an open jar, maggots formed on the meat weeks later. They conjectured that life, in the form of maggots, arose spontaneously from rotting meat. But in 1668, Francesco Redi, an Italian physician and scientist, overturned this idea. He suggested this proof of spontaneous generation was nothing more than contamination of the meat by flies. When flies landed on the rotting meat, they laid their eggs.
Over time, these eggs grew into maggots. Later, the maggots changed into flies. When scientist Redi prevented flies from landing on the meat with a piece of cheesecloth, maggots never formed.
All right, so let's see, I didn't mean to shut that so quickly, but you get the idea here that when Francesco Redi placed the cheesecloth over the the meat, the maggots, the flies weren't able to lay their eggs and the maggots didn't form. So that was the first idea that scientists had that maybe this whole spontaneous generation idea didn't, wasn't going to hold water. But it was really a couple hundred years before the theory was completely debunked. So from 1668, we're going to go all the way to the late 1800s now, and Louis Pasteur, who's, we're going to talk about more in a minute because he's one of our, the first microbiologists, part of the golden era of microbiology.
He devised an experiment that's famous. It's called the swan neck flask experiment, and so I want to play you a little clip describing the swan neck flask experiment so you can understand what Louis Pasteur did that was so revolutionary. Scientists work every day to solve the mysteries of the universe.
Some, though, go their whole careers without solving one frickin'mystery. But others get lucky, or they get creative, and they find answers by trying stuff out. In science, we call this experimentation.
So today, we're gonna look at three biological experiments that changed the world. Number one. The Swan Neck Flask Experiment. In 1862, Louis Pasteur set out to prove that living things did not spontaneously come into existence.
They had to come from some other living thing. Now that seems like a no-brainer to us, but at the time, most people believed in spontaneous generation. The idea that some kind of vital principle in the air caused life to just arise out of nothing.
Pasteur was interested in the newly discovered life form bacteria, and another scientist, Lazzaro Spallanzani, had just proven that bacteria could be killed by being boiled, and if sealed from the air in a container, would not grow back. Regardless of Spallanzani's finding, though, critics argued that boiling just killed the vital principle in the air inside the container. So Pasteur invented an apparatus that he called the swan neck flask.
He designed it so that a sterile liquid could be exposed to the air, but no outside particles like dust or bacteria could get past the curve in the flask's neck. He filled the flask with broth, boiled it and let it sit. Even though it was exposed to the air, the broth never became contaminated with bacteria, proving that air itself had no vital principle.
As a result, the theory of spontaneous generation, enemy of science, was dead once and for all. All right, so there are actually three world-changing biology experiments that Hank Green describes in this video, but we're only interested in the first, we're interested in all of them, but we're only going to listen to the first one. You are more than welcome to... look at this on your own time. He's wonderful in his descriptions.
All right, so we're going to end our conversation about... the spontaneous generation versus biogenesis. We've clearly established that spontaneous generation doesn't work. There's no vital principle.
If you kill all of the living things in the broth and you don't allow any new living things to get in there, nothing will survive. In our next lecture snippet, I'm going to talk about these early microbiologists, including a little bit more about Louis Pasteur.