Today a disease can be investigated by medicine. In the 14th century medicine seemed like it had advanced as far as it could. For instance, each city had a municipal surgeon, a municipal physician, and about twenty private doctors. There were also hospitals and sanitation systems to remove industrial waste. The system seemed novel, but it immediately fell prey to the complexities of the Black Death and quickly proved useless. It did not, for instance, take into account the spread of the disease, through a bacterium in the stomachs of fleas traveling on rats. The doctors of the time never suspected that the disease could be transferred from an animal to a human, and therefore did not take measures to kill the rats or even keep them out of kitchens.
Medicine at that time was dictated by astrology, to which physicians believed all physiology was subject. Bleeding was the most common cure for every sort of disease. There was a rudimentary knowledge of quarantine, which may have helped to some degree, as Tuchman reports:
Stern measures of quarantine were ordered by many cities? Poland established a quarantine at its frontiers which succeeded in giving it relative immunity. Draconian means were adopted by the despot of Milan, Archbishop Giovanni Visconti, head of the most uninhibited ruling family of the 14th century. He ordered that the first three houses in which the plague was discovered were to be walled up with their occupants inside, enclosing the well, the sick, and the dead in a common tomb (Tuchman, pg. 108).
However, the Black Death would revolutionize the medical system. In the High Middle Ages, where there were no major epidemics, the doctors could rely upon ancient teachings and astrology. Because of the plague, doctors were forced to evolve. Eventually this would lead to modern clinical medicine.
The Black Death Part 10: Religion