Ideas About Causes of Disease in 18th & 19th Century (Edexcel GCSE History)

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  • An increase in other, more scientific, explanations like Germ Theory meant that by the 1900s, miasma was an outdated theory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 stated that when matter decays, the process produces microorganisms 

  • Spontaneous generation provided an explanation for 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

A diagram showing how Spontaneous Generation causes 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

A diagram showing how Germ Theory causes decay

• Pasteur’s experiments proved that Spontaneous Generation theory 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

  • Pasteur published his ideas on Germ Theory and disease in 1878

  • 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'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

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

Factors Influencing the Understanding of Disease

A concept map showing factors which helped to progress the understanding of disease in the 18th and 19th centuries