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to some disease-causing organism and destroy it. Ehrlich called such a chemical substance a
“magic bullet.” It seemed that 25 years of work had led him directly to this idea.
During this same period, many specific disease-causing bacteria were being identified
and studied. This gave Ehrlich well-understood targets to attack as he sought ways to create
magic bullets. He chose to start with spirochaete, the microorganism that caused syphilis.
Ehrlich began testing different chemicals using an arsenic base for his compounds. Arsenic
had been effective in destroying a number of other microorganisms.
By 1907, Ehrlich had reached the 606th compound to be tested. He tested this compound on rabbits infected with syphilis. It cured the rabbits. Ehrlich named it salvarsan and
conducted over 100 additional tests to be sure it worked and that it wouldn’t harm human
patients. He then worked for two more years to develop a form of this drug that was easier to
manufacture and that was easier to administer. Of the thousand variations he tried, version
number 914 was the best. He named it neosalvarsan.
Ehrlich’s final test of neosalvarsan was to give it to terminal patients suffering from the
dementia that was the final stage of syphilis. While neosalvarsan helped all of these patients, remarkably, several completely recovered.
Neosalvarsan was the first man-made chemical that would specifically destroy a
target organism and not affect the human patient. This discovery founded the field of
chemotherapy.
Fun Facts: Resistance to antibiotics works by the ordinary rules of natural selection: that segment of the bacteria population that has a natural
ability to counter the drug’s effect will survive, so that their genes eventually are shared by the entire population. Many disease-causing viruses
and bacteria have developed virtual immunity to many antibiotics, making medical planners fear massive disease outbreaks in the near future.
More to Explore
Asimov, Isaac. Asimov’s Chronology of Science and Discovery. New York: Harper &
Row, 1989.
Baumier, Ernest. Paul Ehrlich: Scientist for Life. Teaneck, NJ: Holmes & Meier,
1994.
Dyson, James. A History of Great Inventions. New York: Carroll & Graf Publishers,
2001.
Ehrlich, Paul. Studies in Immunity. New York: John Wiley & Sons, 1990.
Pickstone, John, ed. Medical Innovations in Historical Perspective. New York:
Palgrave Macmillan, 1993.
Zannos, Susan. Paul Ehrlich and Modern Drug Development . Hockessin, DE: Mitchell Lane, 2002.