Louis Pasteur

V

Germ Theory of Disease

Pasteur’s work on fermentation and spontaneous generation had considerable implications for medicine, because he believed that the origin and development of disease are analogous to the origin and process of fermentation. That is, disease arises from germs attacking the body from outside, just as unwanted microorganisms invade milk and cause fermentation. This concept, called the germ theory of disease, was strongly debated by physicians and scientists around the world. One of the main arguments against it was the contention that the role germs played during the course of disease was secondary and unimportant; the notion that tiny organisms could kill vastly larger ones seemed ridiculous to many people. Pasteur’s studies convinced him that he was right, however, and in the course of his career he extended the germ theory to explain the causes of many diseases.

VI

Anthrax Research

Pasteur also determined the natural history of anthrax, a fatal disease of cattle. He proved that anthrax is caused by a particular bacillus and suggested that animals could be given anthrax in a mild form by vaccinating them with attenuated (weakened) bacilli, thus providing immunity from potentially fatal attacks. In order to prove his theory, Pasteur began by inoculating 25 sheep; a few days later he inoculated these and 25 more sheep with an especially strong inoculant, and he left 10 sheep untreated. He predicted that the second 25 sheep would all perish and concluded the experiment dramatically by showing, to a skeptical crowd, the carcasses of the 25 sheep lying side by side.

VII

Rabies Vaccine

Pasteur spent the rest of his life working on the causes of various diseases—including septicemia, cholera, diphtheria, fowl cholera, tuberculosis, and smallpox—and their prevention by means of vaccination. He is best known for his investigations concerning the prevention of rabies, otherwise known in humans as hydrophobia. After experimenting with the saliva of animals suffering from this disease, Pasteur concluded that the disease rests in the nerve centers of the body; when an extract from the spinal column of a rabid dog was injected into the bodies of healthy animals, symptoms of rabies were produced. By studying the tissues of infected animals, particularly rabbits, Pasteur was able to develop an attenuated form of the virus that could be used for inoculation.

In 1885, a young boy and his mother arrived at Pasteur’s laboratory; the boy had been bitten badly by a rabid dog, and Pasteur was urged to treat him with his new method. At the end of the treatment, which lasted ten days, the boy was being inoculated with the most potent rabies virus known; he recovered and remained healthy. Since that time, thousands of people have been saved from rabies by this treatment.

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Pasteur’s research on rabies resulted, in 1888, in the founding of a special institute in Paris for the treatment of the disease. This became known as the Institut Pasteur, and it was directed by Pasteur himself until he died. (The institute still flourishes and is one of the most important centers in the world for the study of infectious diseases and other subjects related to microorganisms, including molecular genetics.) By the time of his death in Saint-Cloud on September 28, 1895, Pasteur had long since become a national hero and had been honored in many ways. He was given a state funeral at the Cathedral of Notre Dame, and his body was placed in a permanent crypt in his institute.

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