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Aetiology (Greek, aitia, ‘cause’ + ology), the study of the causes of disease, was first established when Hippocrates (4th century  BCE) realized that disease was caused not by the actions of the gods but by earthly factors. Several hundred years later, the Greek physician/philosopher Galen ascribed the cause of disease to an imbalance in the four vital humours: blood, phlegm, and yellow and black bile. However, because so many of the causes of disease are unseen, the development of aetiology was delayed until the development of techniques such as microscopy and of knowledge about the principles of genetics. Nonetheless, observations linking causation to pathology were often made: the ancient Egyptians, for example, realized that there was a relationship between a blood-dwelling parasitic worm and the presence of blood in the urine. Furthermore the importance of a ‘sound constitution’ was recognized as important in the avoidance of disease. Modern aetiology encompasses the study of all diseases (genetic, metabolic and immunological, and diseases caused by environmental factors, pathogens, and poor nutrition) and the interactions of different disease states in the affected individual (study of the behaviour of diseases within communities is termed epidemiology). RB
Further reading Andrew Learmouth, Disease Ecology. |
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