Why was there little development in the treatment of disease vetween 1250-1500

There wasn't technology to find way to cure the disease or figure out how it occurred

Leeuwenhoek, in the early 1600s, may have seen the first microorganism in that drop of pond water, but the scientific community did not embrace the idea of microoganisms in the air (or everywhere, as we know they are today) until Pasteur in the late 1800s.

South to get down 2 points