Germ Theory
Germ theory states that many diseases are caused by the presence and actions of specific micro-organisms within the body. Prior to the existence of germ theory, doctors believed that diseases were the result of miasma, a sort of bad air, or imbalance of different components, called humors, in the body. Now, the discovery of microorganisms came well before the understanding of germ theory, but it was only with germ theory that the importance of antiseptics, and later, antibiotics, came into being.
In fact, microorganisms were recognized as early as 1677, Antoni van Leeuwenhoek saw microorganisms through his newly invented microscope. This was the first definitive proof of the existence of life forms too small to see with the naked eye. Leeuwenhoek called these animalcules. When scientists saw these “animalcules” in the blood of individuals with diseases, they believed that they were the result of the illness, not the cause of it.
Before the late 19th century, there was no understanding of germ theory, and, in fact, hospitals were especially dangerous places. A number of different scientists were essential to the understanding of germ theory, including Ignaz Semmelweiss, Joseph Lister and John Snow; however, the research of Louis Pasteur took germ theory mainstream.
Joseph Lister published the first paper on the importance of antiseptics in a medical setting in 1867, advocating the use of carbolic acid as an antiseptic. Semmelweiss had published a paper in 1861 on the issue of puerperal or childbirth fever, noting the risks associated with unclean environments.
While the use of antiseptics dramatically reduced the risk of infection, they did not become widespread until the 1890s. It did not become routine to clean and disinfect surgical tools, operating theaters, or even to wash the surgeon’s hands until around 1900. With the advent of antiseptic procedures and understanding of germ theory, the risk of infection for wounds and surgeries was dramatically reduced. In addition to providing the essential understanding of antiseptics, germ theory was also critical to a thorough understanding of diseases of many different types.