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contagiousness obvious: plague and smallpox could move through a household in a matter of days. But with tuberculosis, when Keats lived with his sick mother and breathed in tuberculosis germs, he remained healthy. It was years late that he became sick.
At the same time, there were those who nevertheless believed that tuberculosis was caused by a contagious agent, a bacterium. The end of the nineteenth century was a propituous time for these scientists. The day had come when they could develop the tools to find such very tiny creatures, even one as small and sly as tuberculosis. The lucky man who would find the tuberculosis bacillus was a young German country doctor named Robert Koch.
Koch was born in a small mining town, the third of thirteen children. Elevn of the children lived to adulthood, a good proportion at the time, when parents could expect infectious disease to kill several of their offspring. So many of Koch's brothers and sisters probably survived because their father ws head of the mine and could afford the best of care. Little did anyone know that nearsighted Robert, who was his mother's favorite, was to bring to the world a means to fight the diseases that routinely killed so many children.
Koch grew up dreaming of adventure, of being a ship's doctor and traveling to unknown lands, but he also fell in love with his childhood sweetheart, Emmy Fraatz, and in teh end gave up his dreams of travel to marry her and settle down as a small-town doctor. His mine never stopped its curious wanderings, however, and soon his home was a collection of specimens taken form the nearby ponds and marshes that he would examine under his microscope. He kept a menagerie of pigeons, dogs, chickens, cats, and foxes. He dabbled in the relatively new field of electrical science, giving patients small shocks to see if i would have a beneficial effect, and delighting his daughter's friends by making their hair stand on end. It was in 1875, after a tour of medical and scientific meetins, that he turned his thoughts to the question some of the best minds in Europe were pursuing: how to find microorganisms that caused disease.
Gerhard Hansen had isolated the germ he believed caused leprosy, but Koch not only would be the first to prove that a microorganism could cause disease, when, in 1876, he found the bug that caused the disease anthrax - a disease of farm animals that can be transmitted to humans - but also would establish the steps scientists have used ever since to show, beyond a doubt, that particu-