From the discovery of anesthetics in the mid-19th century to the battle against AIDS today, human experimentation has been crucial to medical progress. And many times, doctors courageously performed these experiments on themselves.

Among the most celebrated examples of heroic self-experimentation by physicians were the efforts of the U.S. Army doctors at the beginning of this century to discover the cause of yellow fever. Their sacrifices ultimately led to the development of a yellow fever vaccine.

Walter Reed was the Army major in charge of the four military medical researchers who went to Cuba in 1900 to determine how yellow fever was spread. The Walter Reed Army Medical Center in Washington enshrines his memory; the now-disbanded Walter Reed Society of the National Society of Medical Research heralded the vital role of self-experimentation; and for decades, schoolchildren have learned of Reed's exploits in textbooks.

In fact, Reed never experimented on himself. According to the 1987 book on self-experimentation in medicine, "Who Goes First?" by New York Times writer Lawrence K. Altman, much of the glory was a product of the "myth of Walter Reed." He was the only member of his team not to allow himself to be bitten by an Aedes aegypti mosquito, which carries the yellow fever virus, even though he had pledged to do so along with the others, Altman found. Why he did not follow through on his pledge remains a mystery. One of his colleagues, Jesse W. Lazear, died swiftly as a result of his self-experimentation, yet he is all but forgotten today. Only an undergraduate student dormitory at Johns Hopkins University in Baltimore, Lazear's alma mater, is named in his memory.

Yellow fever once was the scourge of much of Latin America and the southern United States. Epidemics swept through Charleston, S.C., three times in the first half of the 18th century. An outbreak in Memphis in 1878 killed about 16,000 people. Between 1793 and 1900, New Orleans alone recorded 41,348 deaths. Sometimes it even reached as far north as New Hampshire. The disease produces a high fever, headache and nausea. It takes its name from the yellow pallor caused by jaundice that patients with severe cases develop after their livers are damaged by the infection.

The cause of this dread disease -- now known to be a virus transmitted by mosquitoes -- long had baffled physicians. Many leading doctors -- Reed included -- believed it was contagious, even though detailed accounts of experiments conducted by researchers as early as 1804 had shown that it was not. And by 1807, John Crawford of Baltimore had become the first to suggest that mosquitoes were the carriers of yellow fever, as well as malaria and other diseases.

It was not until the self-experimentation of the Yellow Fever Commission headed by Reed, however, that the mosquitoes' role in spreading yellow fever was proven scientifically. The disease had so afflicted American forces in Cuba during the Spanish-American War that Surgeon General George M. Sternberg appointed Reed -- then a 48-year-old professor of bacteriology at the Army Medical School -- to lead a research team that included Lazear, 34; James Carroll, 45; and Aristides Agramonte, 32, a Cuban-born physician who may have had a childhood immunity to the disease.

The four physicians first met in Cuba on June 25, 1900, at the Columbia Barracks outside Havana. They spent their initial weeks there studying yellow fever patients and were convinced by what they saw that it was not transmitted by contagion. Aware of earlier studies suggesting the mosquitoes' role in spreading the disease, they decided to test that theory. Soldier volunteers were recruited but the commission members -- all family men with children -- felt morally obligated to risk their own lives as well. Evidently on the night of Aug. 3, 1900, Altman reported, they pledged that each of them would subject himself to mosquito bites and "the same risk that necessity compelled them to impose on others," as Carroll later wrote.

For reasons that remain unknown, Reed left Cuba the following morning, apparently without giving an explanation for his departure.

Lazear and eight other volunteers were the first to allow themselves to be bitten by mosquitoes suspected of carrying yellow fever. None of them became ill. Carroll was the next of the doctors to be bitten by an insect that earlier had bitten a yellow fever patient. Within two days, Carroll came down with a severe case of the fever but survived, albeit permanently weakened. Lazear, either deliberately or accidentally, then allowed himself to be bitten again -- and within five days became fatally ill. He died on Sept. 25. Reed promptly returned to Cuba, and although he never experimented on himself, oversaw the rigorous, subsequent experiments on soldiers that definitively cracked the cause of yellow fever. Nevertheless, it isn't clear exactly why the Army decided to name its great medical center after Reed. Irony may have played a part in that too.

In 1902, Reed was stricken with appendicitis. His physician, William C. Borden, chief surgeon and commanding officer of the Washington Army hospital, hesitated too long about operating -- and by the time he did, it was too late. Reed had developed fatal peritonitis.

Borden later was instrumental in securing congressional approval for the building of a huge modern Army medical center in Washington and presumably had influence on the decision to name it after Reed -- the most famous patient he ever lost. Neil A. Grauer is a writer living in Baltimore. CAPTION: Painting on opposite page depicts Jesse W. Lazear inoculating a patient while Walter Reed looks on from a stairway. A political cartoon from the St. Paul Pioneer Press, above, comments on the success of the U.S. effort against the disease. At left is an Aedes aegypti mosquito. CAPTION: The fame of Walter Reed, above, lives on in large part thanks to the Army Medical Center in Washington that bears his name. But Reed, who led the group of Army doctors searching for a yellow fever vaccine, was the only member of his team who did not subject himself to self-experimentation. Of the other three doctors, one became fatally ill and another permanently weakened.