Overview

Robert Koch was the first scientist to firmly establish the link between germs and disease. A doctor with a small rural practice in Germany, Koch's interest in microscopic studies led him eventually to identify the bacteria that causes the disease anthrax, which was then a common killer of sheep and cows and occasionally farmers. From there, Koch worked to develop the means by which he could prove without a doubt that these organisms were indeed to blame, the basic steps of which are now known as Koch's postulates. According to these postulates, or rules, a microbe may be proved as the cause of a disease if and only if:

• 1) It is found in all cases of the disease.
• 2) It...