- germ theory
1. Pathol. the theory that infectious diseases are due to the agency of germs or microorganisms.2. Biol. biogenesis.[1870-75]
* * *Theory that certain diseases are caused by invasion of the body by microorganisms.Louis Pasteur, Joseph Lister, and Robert Koch are given much of the credit for its acceptance in the later 19th century. Pasteur showed that organisms in the air cause fermentation and spoil food; Lister was first to use an antiseptic to exclude germs in the air to prevent infection; and Koch first linked a specific organism with a disease (anthrax). The full implications of germ theory for medical practice were not immediately apparent after it was proven; surgeons operated without masks or head coverings as late as the 1890s.
* * *▪ medicinein medicine, the theory that certain diseases are caused by the invasion of the body by microorganisms, organisms too small to be seen except through a microscope. The French chemist and microbiologist Louis Pasteur (Pasteur, Louis), the English surgeon Joseph Lister (Lister, Joseph, Baron Lister, Of Lyme Regis), and the German physician Robert Koch are given much of the credit for development and acceptance of the theory. In the mid-19th century Pasteur showed that fermentation and putrefaction are caused by organisms in the air; in the 1860s Lister revolutionized surgical practice by utilizing carbolic acid (phenol) to exclude atmospheric germs and thus prevent putrefaction in compound fractures of bones; and in the 1880s Koch identified the organisms that cause tuberculosis and cholera.Although the germ theory has long been considered proved, its full implications for medical practice were not immediately apparent; bloodstained frock coats were considered suitable operating-room attire even in the late 1870s, and surgeons operated without masks or head coverings as late as the 1890s.
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