SPONTANEOUS GENERATION

Spontaneous Generation was thought to be the Origin of Life until the late 1850s. In 1857, Louis Pasteur noticed that microorganisms were responsible for fermentation (breakdown of an organic compound). In the early 1860s, he proved that fermentation and putrefaction could occur only after exposure to common air. In 1863, he invented pasteurization, a process where fermentation is inhinibited by sterilizing a medium (such as wine) stopping contamination. Pasteur also noticed that some organisms required oxygen to survive (aerobes) and some could grow without oxygen (anaerobes). From this, Pasteur concluded in 1864 that infectious diseases were caused by living organisms called germs.

The most widely accepted notion of infection was the miasma theory. It said that under certain circumstances, air became charged with an epidemic influence which in turn became malignant when combined with the emissions of organic decomposition from the earth. The resulting gases or miasms produced diseases. Supporters of the miasma theory thought that cholera was one disease caused by noxious odours of decayed matter
The second theory was that of spontaneous generation of disease within the blood. This theory was essentially chemical, and denied contagion.
The third notion was the germ theory, or infection was caused by a living organism, a contagium vivum.

People didn't accept the idea that infectious diseases were brought about by an infectious agent (or 'germ') which was passed from one individual to another and caused disease. And it wasn't until people realised that infectious diseases were caused by microorganisms that they could really hope to find a cure for the diseases.

In 1857 Louis Pasteur proved that the air was full of microbes which would grow in the right conditions.

Joseph Lister was a Scottish surgeon who read some of Pasteur's work on germ theory in fermentation and decided that similar 'germs' could cause infection. In 1874 he developed the use of carbolic acid to kill those germs and so prevent infection during and after surgery.