Even in ancient occasions people are unaware on the existence of living organisms invisible for the eye, causing disease. Hence, the ancient Greek scientist and doctor Hippocrates expressed this assumption in one of his works. But come to grips with their study of mankind has been https://www.essaystone.com/ in a position only just after the Dutch optician van Leeuwenhoek inside the XVI century created the initial microscope and saw firsthand the bacteria within a drop of water. Even so, many inside the class scientist denied the existence of pathogens inside several centuries just after the invention of Leeuwenhoek.