As we just discussed, doctors did not believe in bacteria at first. How can an animal live that is so small it cannot be seen?
During the middle ages up until the middle of the 19th century, hygiene was not a priority for anyone. Sewage was dumped in the streets and animals, including hogs, ran freely.
It wasn't until Ignaz Semmelweiss discovered that puerperal fever could be cut by having doctors wash their hands with chlorinated lime, that hygiene was considered at all in medicine. His research was not quick to catch on. He ordered the maternity ward of the ViennaGeneral Hospital in Austria to follow the procedure, and statistical records showed a dramatic lowering in mortality rates (see right of red line in graph blow).
image from Wikipedia
Even though there was empirical data showing that he was correct, doctors still insisted that clean hands and instruments had nothing to do with health, as health at that time was understood to be purely a matter of balance between four "humours" in the body (a theory called dyscrasia), and germ therory was unknown at the time.
It was also considered by some doctors that the idea of being forced to clean hands with chlorinated lime was an insult, as it implied that the doctor's hands were somehow unclean; something which they could not believe at all.
Semmelweiss was driven from his post and eventually found himself working for the Szent Rókus hospital in Pest in Hungary. He held the post for six years.
When he arrived, puerperal fever was rampant in the hospital. Records show that between 1851 and 1855, under his stewardship, there were only 8 puerperal fever deaths out of 933 births. Less than 1%. Between 1841 and 1846, records at the Vienna hospital showed that deaths were very often higher than 10%, and sometimes even 20%, so to keep a rate of lower than 1% in 5 years was a remarkable improvement.
Semmelweiss's discovery was ignored for most of this professional life. It wasn't until Louis Pasteur offered a theoretical explanation for the need for clinical cleanliness that it was accepted. The rejection of new knowledge because it contradicts current beliefs is now known as the Semmelweiss Reflex.