Germ Theory (AQA GCSE History)

How significant was Germ Theory to the understanding of disease? - Summary

Germ Theory was one of the most important breakthroughs in the history of medicine because it finally explained the true cause of disease. Before Germ Theory, many people believed in Spontaneous Generation. However, Louis Pasteur’s experiments proved that germs caused diseases and could spread from one person to another. This was groundbreaking because it ended centuries of misunderstanding about what caused illnesses and provided a scientific explanation that could be tested and observed.

Germ Theory also disproved the beliefs of anti-contagionists. They believed that diseases did not spread through contact but arose from miasma or environmental conditions. With Pasteur's discovery, it became clear that germs were contagious, and illnesses could be prevented by stopping the spread of these microorganisms. This led to better hygiene practices, the development of vaccines, and advancements in public health. Although it took time for Germ Theory to be fully accepted, it transformed medicine by laying the foundation for modern disease prevention and treatments.

Ideas about how disease spread

Miasma

• Many members of society still believed that miasma caused disease

  • The public found miasma easy to understand

  • It explained their observations about poor hygiene and disease

• Scientists who believed that miasma caused disease were called anti-contagionists

Contact

• In the 19th century, there was a growing number of people who believed that disease passed by contact

  • This built upon the existing theory of transference

• Scientists who believed that contact caused disease were called contagionists

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

The principle of Spontaneous Generation

Who was Louis Pasteur?

• Louis Pasteur was a French scientist

• He entered the 1860 French Academy of Science’s competition

  • Scientists were tasked to either prove or disprove Spontaneous Generation

• By 1861, Pasteur had developed Germ Theory

What was Germ Theory?

• Germ Theory states that:

  • air contains microbes

    • Some air has more microbes than others

  • processes like boiling create high temperatures which kill microbes

  • decaying matter did not create microbes, instead, microbes caused decay

The principle of Germ Theory

How did Germ Theory affect Spontaneous Generation?

• 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

Germ Theory and disease

• 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

Applying Germ Theory - Chicken cholera

• In 1879, Pasteur worked on a vaccine for chicken cholera 

• During the work he:

  • identified the germ causing the disease

  • produced a weaker version of the disease

  • treated his patient with the weaker version

• Pasteur proved that treating animals with a weaker version of chicken cholera protected the animals from catching it later

• Pasteur later used this method to create vaccines for other diseases

  • He provided vaccines for anthrax and rabies, both of which impact animals more than humans