Video: How did ideas about the cause of disease change between 1700-1900?

﻿Hello, I'm Ms. Holland and welcome to lesson 10 of Medicine Through Time. So today we are going to have a look at a key turning point in the understanding about the causes of disease. And we're going to look at how germs were finally discovered and the link between germs and disease. So, as usual, if you'd like to take a moment to make sure you have everything you need. For today you'll only need a pen and some paper to make notes with. Make sure that all distractions are turned off. And if you can try and find a nice, quiet place to work where you won't be disturbed. So if you write down today's title, which is How did ideas about the cause of disease change between 1700 and 1900? Okay, and when we're ready, let's start the lesson. Okay, so before we begin, let's see what you can remember about some of our key individuals in a previous lesson. So you have got to decide whether each statement belongs to the Vesalius or Harvey. So number one, discovered that the liver did not produce blood. Number two, studied at Padua University. Number three, proved the human jawbone was in one part. Number four, published "On the Fabric of the Human Body." Number five, dissected human bodies. And number six, discovered that there were valves in the veins. So if you'd like to pause the lesson now, complete the task and then resume once you've finished. Okay, well done. Let's see what we should have got. So number one, it was Harvey that discovered the liver did not produce blood. It was actually the same blood circulating. Two, actually both Vesalius and Harvey studied at Padua University Three, it was Vesalius that proved the human jawbone was in one part, not three as Galen had said. Vesalius also published "On the Fabric of the Human Body" which had all those detailed illustrations of anatomy. Both Vesalius and Harvey said it was really important to dissect human bodies rather than animals. And it was Harvey who discovered that there were valves in the veins, which is why blood flowed in one direction. Okay, so let's have a look, what we're going to do today. We're going to have a look at a new theory called spontaneous generation that came about in the 1700s. We're then going to have a look at two key individuals, the first one Louis Pasteur and his Germ Theory, and the second one, Robert Koch. And then we're going to move on to comprehension questions and our exit quiz. So as we saw in a previous lesson, there were no new ideas about the cause of the disease in the Renaissance, up until 1700. So although the theory, The Four Humours and God had become less popular, as explanations about the cause of disease, miasma was still the most popular belief. However, as microscopes continued to develop in the 1700s, they became more powerful, scientists were able to see microbes, observing rotting matter. This led to a new theory called Spontaneous Generation. So this theory said that decaying matter produced the microbes that they could see under the microscope. And this theory was also closely linked to miasma. And even though no one was able to prove this theory correct, it still took until 1861 to prove it wrong. So pause the video and summarise the theory of spontaneous generation in your own words, then resume once you're finished. Okay, well done. So we just should have something along the lines of, the theory was that decaying matter produced or created microbes or microorganisms. So one of the first individuals we're going to have look at today is Louie Pasteur. So Louis Pasteur was a French chemist and he was actually working in the brewing industry and he was trying to understand why liquids turned sour and went off. So he had previously looked at heating the liquid and found that it killed the bacteria, the microorganisms that you could see under the microscope. This process actually became known as pasteurisation. So if you've ever drank some pasteurised milk, we now know where it comes from. So Pasteur theorised that there were microbes in the air that was causing the liquid to go sour, which is obviously the opposite of the spontaneous generation theory. So to prove his theory, Pasteur conducted the swan neck flask experiment. And it's called this because as you can see on the image on the slide, the neck of the glass was in the shape of an S. Pasteur said that this S shape would prevent air from reaching the liquid inside the flask. So the flask was filled with a broth and then it was heated to kill any microorganisms that were already present. Pasteur observed the liquid did not go off and had no microbes growing in it. He also named these microbes germs. However, when he repeated the experiment, but then broke the neck the flask before the bend, which you can see on the second image on the slide, the liquid, which had been in contact with air did go off and had microbes growing in it. So, Pasteur had proved that there were germs, there were microbes in the air, and that these caused matter to go off and decay. He called this the Germ Theory and he published it in 1861. But he did begin to think that germs in the air could be the cause of disease in humans too. Later on Pasteur carried out further experiments whilst working to help the French silk industry. So he was looking at why so many silkworms were dying of a disease, and he was able to prove that it was being caused by a microbe in the air. So in 1878, he then published his Germ Theory of infection, linking the Germ Theory to human illness. Therefore, it had an application to medicine. So pause the video now and have a go at describing the swan neck flask experiment in your own words. You might want to use the image on the slide to help you. Then resume once you're finished. Okay, well done. So remember, the experiment was that when liquid was heated and it wasn't exposed to air, it didn't go off, but when it was heated, but then exposed to bacteria, microbes were present. So did Pasteur's Germ Theory revolutionise understanding about the causes of disease? Well, not straight away. Even though he had proven that germs existed in the air and caused decay, the Germ Theory did not lead to change immediately. So many scientists and doctors actually refused to believe that microbes in the air could cause disease and they discredited Pasteur's work because he wasn't a doctor either. And also Pasteur's theory had not explained how the microbes made people ill, or even which microbes caused specific diseases, which made it even more difficult for people to accept his ideas. A key example of opposition was someone called Dr. Henry Bastion. He was a really well known and powerful influence in medicine in Britain. He criticised Pasteur's theory for the rest of his life and refused to accept it. Instead, he continued to promote the theory of spontaneous generation. So in Britain, there was little change in the understanding of the cause of disease until the late 1870s at least, because he was such an important influence. However, not everyone criticised Pasteur, for example, Lister and Tyndall both accepted and used the Germ Theory in their work. For example, Joseph Lister, who you'll learn about in a later lesson, applied the Germ Theory to his work on infection following surgery. And John Tyndall also promoted Pasteur's work in 1870. He supported the idea that there were microbes in the air, and even suggested that dust particles carried those microbes in one of his lectures. So pause the video in a minute to complete the following task. Explain how the Germ Theory is different to the theory a spontaneous generation. Then resume the video once you're finished. Okay, well done everyone. So it's basically the opposite of each other. Spontaneous generation was a theory that decay caused microbes, and the Germ Theory was the idea that microbes caused decay. So, let's move on to look at our second individual for this lesson, and that is Robert Koch. So Robert Koch was a German microbiologist and he was working on developing Pasteur's ideas. And he was important because he was able to successfully identify and isolate the microbes causing specific diseases. So for example, in 1876 he was able to discover the microbe that caused anthrax, and he tested his ideas on mice. In 1882 he discovered the bacteria causing tuberculosis, which was quite a horrible disease at the time. In 1883, he discovered the microbe that was causing cholera. And he further proved this in 1884 whilst working in Calcutta in India. So Koch was able to do this, to isolate the microbe causing the disease by using the following method, which became known as Koch's postulates. So he would isolate a microbe that was present in different cases of a singular disease. So looking for a common similarity. He would then grow this microbe in a controlled environment and test it on animals to try to reproduce the disease. The microbe would then be taken from the diseased animal and grown again, being identical to the original culture. And if it was identical, this then proved that the microbe that had been isolated and grown and regrown was the one that was causing that specific disease. So more importantly, Koch's work proved the Germ Theory correct, that it was microbes causing some diseases. So after Koch's work into microbes, Pasteur's theory began to become more accepted. And that's really really important to remember. Koch also developed ways to make it even easier for scientists to identify and isolate the microbes causing specific diseases. For example, he developed agar jelly to grow bacteria in a more controlled way, and it was also easier to observe under a microscope. You've probably even used agar jelly in one of your science lessons when they're on the Petri dishes. He also developed a dye to stain the disease causing microbe again, making it easier to study and more visible. So, we're going to have a go now at trying to put the events about how ideas changed about the cause of disease into chronological order. So on the slide you have got several different events that you need to try and put in the correct order. I have already given you the first one, which is the first recorded observation of bacteria. So if you'd like to pause the video now, have a go at the task and then resume once you're ready. Okay, well done everyone. Let's go through the answers. So we've already said our first one is the first recorded observation of bacteria, and that was in 1683. We then should have had the development of the spontaneous generation theory in the early 1700s, once microscopes become more powerful. Then Pasteur publishes Germ Theory in 1861. Then Koch discovered the microbe that caused tuberculosis and then cholera in 1882 and 1883 respectively. And then finally, Koch developed a dye to make it easier to isolate the disease causing bacteria, and this was in roughly 1885. Really well done on that task everyone. So let's finish by having a look at what the impact of our two key individuals today. So if we have looked first at how they helped cause change. So the work of Pasteur and Koch was important because it finally disproved miasma and spontaneous generation. It was an accurate explanation of disease, finally. It also led to the causes of more diseases being understood. For example, in Britain in 1883, the microbe that caused diptheria, which is a really dangerous bacterial infection, was discovered thanks to Koch's work. Scientists were also able to discover ways of trying to either kill or vaccinate against the microbe causing diptheria and other diseases, rather than trying to just treat the symptoms of it as had been done in the past. So by 1900, it was accepted that germs were a cause of disease. Koch's work influenced Pasteur, and he began to work on creating vaccinations. So vaccinations protect you against a disease, they give you immunity. And he did this to begin with for chicken cholera and then anthrax, using weakened strains of the microbe that caused the disease. So both individuals inspired other scientists to not only study microbes, but also develop vaccinations, which you will see again in later lessons. However, there were some limitations of their work. The work of Pasteur and Koch took a long time to be accepted, even by the British government. For example, in 1884 in India, Koch was proving that cholera was caused by microbes in the water, but the British government refused to believe it and still reverted back to miasma. And you will also see of the outbreak in cholera in England that the British government, again, refused to believe that it was germs. And there were also some illnesses and diseases which could not be explained by the Germ Theory, which would not be addressed until the modern period. So let's have a go at our comprehension questions now. We'll read them through together and then you can pause the lesson and use the worksheet to help you answer them. So question one, why do you think it took so long for somebody to disprove the theory of spontaneous generation? Question two, explain why the Germ Theory was not accepted until Koch's work in the 1880s. Number three, why was the Germ Theory a turning point in the understanding of the cause of disease? Number four, can you describe the process used by Koch to identify disease causing microbes. Number five, how far do you agree the work of Pasteur was more significant then the work of Koch in changing ideas about the cause of disease from 1700 to 1900? And you can use the sentence starters there to help you if you would like to. Pause the lesson now. Okay, well done everyone for having a go at those questions. Let's go through the answers. As usual, don't worry if you haven't got everything that I have word for word, but if you can check your answers as we go through and give yourselves a nice big tick. Okay, so why did it take so long for somebody to disprove spontaneous generation? You could of said that microscopes needed to be stronger and the theory of miasma was very popular, so it was going to be hard to kind of move away from those older theories. You could have said though, for better answer, there was a reluctance to challenge the theory of miasma, which is obviously linked closely to spontaneous generation, as it was a popular belief even with the British government. Technology was also still developing, and by the mid 1800s scientists were only just beginning to see magnified enough images to begin to develop new ideas and question spontaneous generation. Number two, why was the Germ Theory not accepted until Koch's work in the 1880s? You could have said that Pasteur hadn't been able to explain how microbes in the air caused disease, or which ones. For a good answer let's go into a little bit more detail. So Koch was able to identify and isolate microbes causing diseases and replicate this in his methodology. He proved the Germ Theory was correct, and that it was microbes in the air causing some disease. Question three, why was the Germ Theory a turning point in the understanding of the cause of disease? You could have simply said it proved old theories like miasma wrong. But for a good answer, again I'd have a bit more detail. It proved the inaccurate theories of miasma and spontaneous generation wrong. The theory was accurate and based on scientific proof. The Germ Theory, eventually, led to scientists identifying many different diseases caused by microbes, and it also led to further vaccinations being developed. Question four, can you use the process used by Koch to identify disease causing microbes? You could have said that he identified the microbe by looking at which one was present in all cases of the disease, so looking for those similarities. But if you go into more detail about Koch's postulates, so the microbes present in every case of the disease would be identified and then grown in a culture. It would be tested on an animal to see if they contracted the disease. The microbe would then be taken from the animal to make sure it was identical to the original isolated microbe to make sure they had the right one. And question five, how far do you agree the work of Pasteur was more significant than the work of Koch in changing ideas? So you could have said that we agree Pasteur was more important because he was the one that proved germs caused decay and then theorised that they caused disease. And he proved they were all around us in the air. The identification of microbes as a cause of decay, then allowed Koch to develop his work into isolating the ones that caused diseases. So you could argue that without Pasteur's work Koch wouldn't have been able to complete his work on identification and isolation. And also several key individuals supported Pasteur's theory, so it did have an impact on some aspects of medicine at the time. We could disagree. We could say that Pasteur's theory lacked proof until Koch was able to isolate the microbe causing a specific disease. That Koch's methods of growing and staining microbes was significant in allowing other scientists to also study microbes. Then we could also say that Koch's work led to the diseases themselves being studied, rather than the symptoms. So therefore these were reasons why it could be argued that Koch was more significant. So let's return to our big picture. If we have a quick recap of our previous two time periods, we saw that the mediaeval period, there was little change, pretty much no change in the understanding of the cause of disease. Then the Renaissance period, there was some change in the understanding of the cause of disease, but this change was fairly slow. So, some people started looking for scientific explanations, but there was still a lot of traditional attitudes within society. So where does our industrial period go? What do you think? So what do you think? You might have thought that it was slightly different than our other two periods, because there was a greater amount of change, but it wasn't for the whole time. So it might look something like this. There was a significant amount of change, but only really in the last 40 years of this period, so after 1861, because the Germ Theory was a turning point, but really it wasn't accepted straight away. So we could even say that that rapid change was only from the 1880s onwards. And before the Germ Theory we're lower down on the timeline, because there were very few new ideas about the cause of disease other than spontaneous generation, which was inaccurate. So fantastic lesson everyone, really well done. We have now studied one of the really big turning points in the understanding of the causes of disease. So next lesson, we are going to be having a look at why the discovery from this lesson was actually possible. So don't forget to keep all of your notes together. Okay, so don't forget to take the exit quiz now. And if you'd like to, please ask your parent or carer to share your work on Instagram, Facebook, or Twitter, tagging @OakNational and #LearnwithOak.

Worksheet: How did ideas about the cause of disease change between 1700-1900?

Exit Quiz: How did ideas about the cause of disease change between 1700-1900?

Completed: How did ideas about the cause of disease change between 1700-1900?

A study of the Germ Theory and the work of Pasteur and Koch in changing the understanding about the causes of disease.

History

Y10 History

Key Stage 4

Year 10

Miss

How did ideas about the cause of disease change between 1700-1900?

Medicine through time, c.1250-present day

UNIT

How much medical progress did ancient Greece and Rome make?

What did people think about where disease came from in medieval Britain?

How did people in medieval times try to prevent and cure diseases?

Who did people go to for medical help in medieval times?

What can the Black Death tell us about medieval medicine?

How much medical progress was made during medieval Britain?

Why was there greater medical progress between 1500-1700?

Why did ideas about causes of disease change between 1500-1700?

How did individuals change medical understanding between 1500-1700?

Why did ideas about the cause of disease change between 1700-1900?

How did ideas about causes of disease change after 1900?

How quickly did ideas about causes of disease change and why did ideas change over time?

Did ideas about prevention and treatment change between 1500-1700?

How did approaches differ in dealing with the Great Plague compared to the Black Death?

When did vaccination really start to make a difference to health in Britain?

How far did John Snow change ideas about the prevention of disease?

How and why did ideas about responsibility for public health change?

How did hospitals change over time and improve prevention and treatment of illness and disease?

Why were there improvements in surgery?

Did the NHS transform medicine in Britain?

How far did treatment advance in the 20th century?

How important was the role of chance in the discovery and development of penicillin?

How has the use of science and technology changed ideas around the treatment and prevention of lung cancer?

How quickly did ideas about prevention and treatment of disease change and why did ideas change over time?

How were trenches designed and why did battles on the Western Front lead to medical advancement?

What medical conditions were there on the Western Front?

How far did war on the Western Front give rise to new techniques in medical treatment?

How were wounded soldiers helped on the Western Front?

How far did WW1 accelerate medicine and treatment in the 20th century?

History

How did ideas about the cause of disease change between 1700-1900?

Video

Worksheet

Final Quiz

Lesson Complete