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What is scientific medicine?

Published: 23 July 2019

Medicine has always involved skills we recognise as scientific and empirical methods: doctors make observations, record their results, look for patterns, they develop theories about the health with their patients or the causes of a disease and they carry out experiments to test their theories.

For centuries, Western medicine was hugely influenced by the humoral system, developed by the ancient Greeks. Based on a theory of balance of four bodily fluids: black bile, yellow bile, phglem and blood in the body, these ideas gave physicians a framework for making rational and consistent medical decisions. Humoral thinking was influential on how people understood their bodies in health and illness. 

But in the 1800s, new scientific disciplines and methods emerged that would radically change the way medicine was practised. Then, as science and medicine developed further, a whole host of new biological and life sciences became established in the 1900s.


Engraving of Galen Wellcome Collection (CC BY) Image source for Engraving of Galen
Line engraving of Galen by G P Busch

Anatomy is perhaps the oldest of medical investigations. In the 100s, the Greek physician Galen carried out animal dissections in order to investigate the inner structure of the body, but for centuries human dissection was hampered by social and religious taboos against tampering with the dead.

At the end of the 1400s, the Renaissance anatomist Andreas Vesalius urged physicians to conduct human dissections and make their own observations, rather than rely on animal dissection or trust descriptions handed down through ancient and often unreliable texts attributed to medical authorities (such as Galen). His anatomical atlas, ‘On the Fabric of the Human Body’ was hugely influential and spawned many imitations as later anatomists followed his example.

The work of anatomical researchers such as the English physician William Harvey, who devised experiments to prove that blood was circulated around the body by the heart in the 1600s, gave doctors an increasingly detailed understanding of the structure of the human body.

Second edition of 'De humani corporis fabrica' by Vesalius, published in Basel, Switerland, 1555
Science Museum Group Collection More information about Second edition of 'De humani corporis fabrica' by Vesalius, published in Basel, Switerland, 1555

The laboratory sciences

Laboratory sciences gave us a way of understanding diseases caused by bacteria and viruses and how they impact our health. New tests using blood and urine gave doctors new tools to inform their diagnosis. Every major hospital around the world now has its own laboratories.

One of the biggest influences on scientific medicine was the development of the microscope in the 1600s. Investigations of micro-organisms by Royal Society members Antoni van Leeuwenhoek and Robert Hooke were the forerunners of modern life sciences such as bacteriology and cell science. But it took another 200 years before microscopes were routinely used in medical sciences and biology.

Rudolf Virchow and cell science

Rudolf Virchow

In the 1830s, two German scientists, Theodore Schwann (1810–1882) and Mathias Schleiden (1804–1881) proposed that cells were the building blocks of life. The idea was taken up and developed by another German researcher, Rudolf Virchow (1821–1902). 

Virchow’s work put the microscope at the centre of pathological science, the study of diseased cells and tissue. His book ‘Cellular Pathologie’ showed how cells were the fundamental units involved in processes such as  the spread of cancer. He also established that cells regenerated through cell division. 

Virchow’s research began in the laboratory, examining tissue and cells under the microscope. He would then relate his findings to what he learned from observing and treating patients in the hospital. 

Although his work with microscopes was groundbreaking, Virchow did not accept the other major medical theory of the 1800s, the germ theory of disease.

Louis Pasteur and microbiology

The celebrated French scientist Louis Pasteur was probably the first microbiologist.  He was interested in what we would now call microbiology—the study of microorganisms.

He worked in industry and agriculture, investigating the role of yeasts and other organisms in fermentation. He investigated an infectious disease in silkworms for the French silk industry. And the process he developed for sterilising liquids such as milk was named pasteurisation after him. 

Brass microscope Science Museum Group Collection Image source for Brass microscope
Compound monocular microscope used by Pasteur

Pasteur had no medical training but based on his work with microorganisms he proposed the germ theory of disease—the idea that diseases might be caused by microorganisms infecting the body. His research on germ theory began with another agricultural problem: anthrax, an infectious disease of people and animals. 

Pasteur identified the anthrax bacterium by examining blood smears from infected subjects under the microscope. He then set about developing a vaccine based on an attenuated (weakened) strain of the bacteria. He announced his success in a very public demonstration of the vaccine by infecting vaccinated and non-vaccinated animals with anthrax. The vaccinated animals survived.

Pasteur also developed a vaccine for rabies. This was a greater challenge than anthrax because rabies is caused by a viral infection that Pasteur could not see under his microscope, since viruses are so small.

However, the symptoms of rabies pointed to an infection of the nervous system, so Pasteur used the spinal cords of rabbits to isolate the viral infection by filtration. He was able to develop a vaccine from this fluid.

Thanks to his rabies vaccine, Pasteur became something of a celebrity and his work convinced many people of the value of his research. 


Robert Koch and bacteriology

Robert Koch was a generation younger than Pasteur and a doctor as well as a scientist. He drew early attention to his research by identifying the bacterium responsible for causing tuberculosis. For a disease that many did not even recognise as infectious, Koch’s discovery was impressive. For his work, Koch was awarded the 1905 Nobel Prize for Physiology or Medicine. 

Koch also identified the bacterial cause of cholera and determined that it was transmitted by an oral-faecal route. Most of his laboratory research on cholera was done in 1883-1883 in India where cholera was endemic (or regularly found in a certain place). 

Robert Koch (seated) and Richard Pfeiffer working in a laboratory, investigating the plague in Bombay, 1897.

He was a gifted laboratory scientist. He developed and improved laboratory equipment such as photomicrography (photography of objects under a microscope) and the use of agar-agar as a growing medium for bacterial cultures. One of his students, Julius Richard Petrie, developed the Petrie dish to grow cultures in.

By the end of the 1800s the germ theory of disease was established and researchers shifted their attention to identifying specific causative agents for specific diseases. Koch devised a set of criteria for confirming that a microorganism was the cause of a particular disease. They were described as Koch’s postulates by one of his students:

  1. The organism must be shown to be constantly present in characteristic form and arrangement in diseased tissue.

  2. The organism which from its behaviour appears to be responsible for the disease must be isolated and grown in pure culture.

  3. The pure culture must be shown to induce the disease experimentally.

Koch’s postulates are still taught to medical students and continue to be the basis of disease classification, although characterising a disease in the real world is rarely as straightforward as the postulates suggest. 

Claude Bernard and physiology

Physiologists applied the sciences of chemistry and physics to understanding how the body worked. The German chemist Carl Ludwig (1816–1895) of the University of Leipzig used his experiments and measurements to argue that the human body could be understood in the same way as any other natural system and that the same physical and chemical laws applied to living bodies.

The French physician Claude Bernard was a professor of physiology in Paris and developed rules for experimentation in medicine of rigorous experiment and observation. His experiments shed light on the process of digestion and the function of organs such as the liver and nerves. 

Much of Bernard's work was based on vivisection—experimenting with living animals. Many people opposed this method, including Bernard's wife and daughters, who argued with him over their support for the anti-vivisection movement.

Oil painting of Claude Bernard and his pupils, 1889.

Bernard published his recommendations for the use of experimental method in a very influential work, ‘An Introduction to the Study of Experimental Medicine' (1865). In the book, he outlined the three pillars of experimental medicine:

  • Physiology, which dealt with normal function
  • Pathology, which investigated abnormal function 
  • Therapeutics, which centred on developing treatments

Medical technology

Medicine and the medical sciences were reliant on technological advances, particularly from the the 19th century. The microscope transformed laboratory sciences, and the technology to give continuous graphical readings of bodily functions was invaluable in physiology but also impacted clinical practice.

Blood and urine tests have also given doctors ways of diagnosing their patients’ health, including preventative measures such as screening for cervical cancers using a microscope. 

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Suggestions for further research


  • B Latour and S Woolgar, Laboratory Life: The Construction of Scientific Facts, 1986
  • W F Bynum, Science and the Practice of Medicine in the Nineteenth Century, 1994
  • C Lawrence, Medicine and the Making of Modern Britain, 1700-1920, 1994
  • A Wear, (ed.) Medicine in Society, 1992