: the study of the essential nature of diseases and especially of the structural and functional changes produced by them
: the anatomic and physiological deviations from the normal that constitute disease or characterize a particular disease
: a treatise on or compilation of abnormalities <a new pathology of the eye>
Medical specialty dealing with causes of disease and structural and functional changes in abnormal conditions. As autopsies, initially prohibited for religious reasons, became more accepted in the late Middle Ages, people learned more about the causes of death. In 1761 Giovanni Battista Morgagni (1682–1771) published the first book to locate disease in individual organs. In the mid-19th century the humoral theories of infection were replaced first by cell-based theories (seeRudolf Virchow) and then by the bacteriologic theories of Robert Koch and Louis Pasteur. Today pathologists work mostly in the laboratory and consult with a patient's physician after examining specimens including surgically removed body parts, blood and other fluids, urine, feces, and discharges. Culturing of infectious organisms, staining, fibre-optic endoscopy, and electron microscopy have greatly expanded the information available to the pathologist.