Syllabus Edition
First teaching 2024
First exams 2026
Ideas About Causes of Disease in 18th & 19th Century (Edexcel GCSE History)
Revision Note
Written by: Zoe Wade
Reviewed by: Bridgette Barrett
Developments in Ideas about Disease in the 18th and 19th Centuries - Timeline & Summary
There was significant progress in understanding the causes of disease in the 18th and 19th centuries. This era is sometimes called the ‘Scientific Revolution’ when new ideas replaced existing beliefs. There was a vast improvement in scientific technology. For example, 19th-century microscopes were able to magnify images without blurring. Scientists could examine microbes (microscopic organisms) in more detail than ever before. The most important event of this period was Pasteur’s Germ Theory. It explained how germs caused decay. Robert Koch, Pasteur’s competitor, developed Germ Theory further. In his work, Koch explained how different germs are responsible for specific diseases like tuberculosis. The work of Pasteur and Koch was critical in improving disease prevention and treatment. Germ Theory met with strong resistance from scientists and the public. They did not want to abandon well-established theories such as Spontaneous Generation or miasma. The government had a laissez-faire attitude to the health of the people. This is French for ‘allow to do’, it means not to interfere and let people make their own choices. This didn’t change until the 1870s. With increasing evidence and successful practical application (for example, Joseph Lister using Carbolic Acid), scientists and the public accepted Germ Theory as the correct explanation for the cause of disease. |
Miasma
Many members of society still believed that miasma caused disease
The public found miasma easy to understand and it explained their observations about poor hygiene and disease
Towards the end of the 19th century, miasma became less popular as an explanation for disease
An increase in other, more scientific, explanations like Germ Theory meant that by the 1900s, miasma was an outdated theory
Spontaneous Generation
Scientists developed Spontaneous Generation theory in the early 18th century
The theory states that, when matter decays, the process produces microorganisms
Spontaneous generation explained the microbes on decaying matter which scientists could see using a microscope
Scientists also stated that microbes spread through miasma, linking their new ideas to a well-known and trusted explanation
Spontaneous generation was just a theory
Scientists did not have the evidence to prove that decay caused germs
Worked Example
Describe one feature of Spontaneous Generation
2 marks
Answers:
Spontaneous Generation suggested how germs were created (1). It stated that decaying matter created microbes as a product of the process of decay (1).
Examiner Tips and Tricks
This question previously asked students to describe two features of a given event. This question was out of four marks. However, as of 2025, Edexcel will split this question into two subsections, asking you to describe a feature of two different events. Each subsection is worth two marks.
Ensure you make your details as specific as possible to access all 2 marks. The details of this example include the keyword of 'decay'.
Pasteur and Germ Theory
Louis Pasteur and the development of Germ Theory
Louis Pasteur was a French scientist
He entered the 1860 French Academy of Science’s competition to either prove or disprove Spontaneous Generation
By 1861, Pasteur had developed Germ Theory which stated:
Air contains microbes
Some air has more microbes than others
Processes like boiling create high temperatures which kill microbes
Decaying matter didn’t create microbes, instead, microbes caused decay
Pasteur’s experiments proved that Spontaneous Generation was incorrect
Pasteur observed that microbes would not grow on sterilised matter which was left in an airtight container
He concluded that something in the air must cause matter to rot
Pasteur also believed a link between germs and disease existed
In 1870, Pasteur released a report based on his germ theory
The report was on an epidemic disease killing silkworms in France
Silkworms were vital to France’s prosperous silk industry, worth 130 million Francs in 1853
Pasteur published his ideas on Germ Theory and disease in 1878
Examiner Tips and Tricks
Many students get confused about Spontaneous Generation and Germ Theory. Try to remember that they are opposite to each other. Germs are created from decay in Spontaneous Generation whereas germs create decay in Germ Theory.
Pasteur's Influence in Britain
Spontaneous Generation remained a popular theory in Britain until the 1870s
Many doctors like Dr Henry Bastian supported Spontaneous Generation rather than germ theory
Doctors were trusted members of society which meant the public also refused to link germs to disease
Some scientists supported Pasteur’s ideas including:
Joseph Lister - he linked Germ Theory to the issue of infection after surgery
Lister could not prove his theory as some microbes are good for example those in the gut
John Tyndall linked the discovery of particles in the air to Germ Theory
Tyndall was a physicist, not a doctor which meant many medical professionals ignored his suggestions
Examiner Tips and Tricks
From c.1250-present, the public blocked new developments in ideas, treatments and prevention of disease. For example, in the Renaissance, people continued to believe the Theory of the Four Humours when medical professionals knew this was incorrect. This is similar to the public clinging onto the idea of miasma instead of embracing Germ Theory. Public attitudes were a major factor in slowing down the speed of change across this course.
Koch and Bacteria
Robert Koch's Work on Microbes
German scientist Koch successfully linked germs to disease
In 1882, he discovered the bacteria responsible for tuberculosis
In 1883, he discovered the cholera bacteria
In 1884, he confirmed water spread the disease
John Snow had theorised this nearly 40 years before Koch in his work on cholera but couldn’t prove it
Koch revolutionised bacteriology (the study of bacteria)
He inspired scientists to continue the hunt for bacteria that caused diseases such as diphtheria (a serious infection in the nose and throat which causes difficulties in breathing and swallowing) and plague
This led to these diseases becoming preventable meaning they killed fewer people
Koch developed techniques that made microbes easier to see under a microscope:
He promoted the use of agar jelly (a substance derived from algae) to grow bacteria
He also stained the bacteria in dye
He received the Nobel Prize for Medicine in 1905
Koch's Influence in Britain
Koch’s work was a breakthrough in the identification and treatment of disease
Scientists recognised that the treatment of the bacteria was required rather than the treatment of the symptoms
In the case of diphtheria, scientists observed that the bacteria created a poison that, when breathed in, remained in the throat
It was this bacteria which was responsible for the swallowing and breathing difficulties
Some still doubted the importance of Koch’s discovery
The British government ignored Koch’s work on cholera being waterborne
The government still believed that miasma spread the disease
Worked Example
Explain one way in which ideas about the cause if illness in the years c1250-c1500 were different from ideas about the cause of illness in the 18th and 19th century
4 marks
Answers:
One way in which the ideas about the cause of illness were different from the medieval period to the 18th and 19th centuries was miasma (1). In the medieval period, miasma was seen as a key explanation for illness (1), for example, people stayed away from swamps, corpses and rotting objects to avoid becoming ill (1). However, towards the end of the 19th century, miasma became a less popular belief. By the 1880s, Pasteur and Koch explained that microbes were responsible for making people ill (1).
Examiner Tips and Tricks
The 19th century marked a turning point in the ideas about disease. Due to scientific breakthroughs, this is a significant period of change from the medieval and Renaissance periods. Finally, the technology and expertise were available to disprove old beliefs and support correct, science-based theories about the cause of disease. Remembering this will help you in your exam answers.
Factors Influencing the Understanding of Disease
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