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Veterinary thermometer, England, 1950-1978

Veterinary thermometer, England, 1950-1978

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Unique to normal: the approach of doctors to patients

What is normal? Scientific medicine today tells us how much we should weigh, what our blood pressure should be, and whether our height or the quality of our eyesight count as disabilities. These standards are supposed to be universal, but ancient and medieval physicians once argued that every patient was unique. It was the task of the skilful physician, they said, to prescribe cures that were suited to the individual case.

The causes of differences: the investigation in the Enlightenment

Before the rise of scientific medicine, people didn’t consider malformations as medical problems in need of correction or treatment. Instead, malformations in humans and animals were interpreted as signs from God, or as evidence of the playfulness of Nature. In the Enlightenment, researchers began to investigate what caused these differences, arguing that their research would also shed light on how healthy bodies are formed. From about 1800, anatomists and universities created collections of these interesting pathological specimens for research and teaching.

How to define normality?


The word ‘normal’ was originally a mathematical term - in fact it wasn’t applied to humans until the 1800s. Normality could be defined in two ways: qualitatively and quantitatively. Qualitatively, you could compare a body part to a specimen or a model which showed what the normal state should look like. Examples from the Science Museum's collection are the model of a horse and the retina models used for the training of doctors with the ophthalmoscope. When, in the 1800s, measurement became important for medicine, this approach led to another, quantitative definition of normality.

Adolphe Quetelet - statistics and society

Statisticians such as Adolphe Quetelet began to apply statistics to society. He defined the ‘average man’ against which individuals could be judged. Clinicians used their access to large numbers of patients in hospitals to establish ‘normal’ values for physical features, such as temperature and blood pressure.

Francis Galton’s attempts at defining normality


The English scientist Francis Galton (1822-1911), a cousin of Charles Darwin, used both qualitative and quantitative approaches to define normality. With composite photographs he attempted to establish types of criminals and diseases. He superimposed photographs of large numbers of criminals and other abnormal persons, thinking that this would result in images of ‘abnormal types’. To his surprise, he found that the composites of these ‘abnormals’ tended to look just like everyone else.

How does one define normality?

Definitions of normality make medical diagnosis easier, but they also bring with them a number of problems. It is not obvious how the normal should be defined. In the case of body temperature, for instance, researchers have proposed a number of ranges for what should count as normal. Different medical encyclopedias give different temperatures.

The negative effects of defining normality


Definitions of normality can also have far-reaching social consequences. Galton, for instance, developed the notion of eugenics, the idea that the human race could be improved through breeding if only ‘normal’ people were allowed to have children. This idea was taken up in many countries in the early 1900s, including the UK, the US, Germany and Sweden. But eugenics initiatives have led to the forced sterilisation and even murder of ‘non-normals’. During the Cold War, the American civil service used lie detectors to search for homosexuals among its employees, who were considered ‘non-normals’ and therefore potential threats to national security. Today, activists continue to raise awareness about the negative effects of definitions of normality.


R Bud and D J Warner, (eds) Instruments of Science: An Historical Encyclopaedia (New York and London: The Science Museum, London and The National Museum of American History, Smithsonian Institute. Garland Publishing, 1998)

G Canguilhem, The Normal and the Pathological, translated by CR Fawcett; with an introduction by Michel Foucault (New York, Zone Books, 1989)

W Ernst, (ed.), Histories of the Normal and the Abnormal (London: Routledge, 2006)

M Hagner, 'Enlightened monsters', in The Sciences in Enlightened Europe, W Clarke, J Golinski, and S Schaffer, (eds) (Chicago: Chicago University Press, 1999)

D J Kevles, In the Name of Eugenics: Genetics and the Uses of Human Heredity (Cambridge :Harvard University Press, Mass. 1995)

P M H Mazumdar, Eugenics, human genetics, and human failings: the Eugenics Society, its sources and its critics in Britain (London and New York: Routledge, 1992)

J Knoper, 'The thermometer: history and application in veterinary medicine', Veterinary heritage: bulletin of the American Veterinary History Society, 16/2 (1993) pp 51-60



The study of human improvement by selective breeding, founded in the 1800s by English scientist Sir Francis Galton. Widely discredited after its use by the Nazi regime.