Primitive peoples believed that evil spirits carried diseases. Hebrews and Greeks proved that cleanliness protected them from many ailments. In the Middle Ages doctors ascribed to various invisible contagia the causes of diseases. In 1658 by means of a simple microscope Athanasius Kircher of Fulda, Germany, saw "worms" in the blood of people stricken with Black Plague. Those probably were the first germs ever noted. As microscopes were improved more kinds of animalcula were observed, and doctors gradually associated them with disease. But not until 1876 was a germ proved to be a...
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