Its ravages had been endured with hopeless despair, with no chance to escape but in flight; and, often, flight was denied to those who lived in the stricken districts. Quarantine was rigidly enforced. So terrified were those who lived in the uninfected regions, that refugees from yellow fever cities were turned back by loaded shot-guns.

Household goods were destroyed, bedding and clothing and even houses were burned, to prevent the spread of the disease. Yet it was only held in check, and the people continued to live in terror of it. Just the announcement that yellow fever had appeared in a town was enough to make the bravest heart turn sick with the awful consequence of the horror it might mean.

Yellow fever had always been present in Cuba. Ships from that island brought it into Southern cities, and the contagion, once started, went on its ravages for months at a time. When Cuba was occupied by the United States, the problem of the yellow fever was in the hands of our Government.

Our soldiers were going into Cuba, and it was said that those who went would sooner or later have the fever. Many lives were thus imperilled. It was for our Government to find out what measures could be taken to save the men.

A Board of Medical Commissioners was appointed to go to Cuba and investigate the yellow fever. Of this Board, Major Walter Reed, an army surgeon, was appointed chairman. Major Reed had never had the fever, but he was too brave an officer and too devoted a surgeon to do otherwise than welcome this opportunity for service.

He had to deal with a treacherous enemy, that stalked up and down in the dark, attacking its unsuspecting victims. No one knew how it came, or by what means it spread. It was found wherever filth and darkness prevailed, and was sup-posed to be a filth disease.

"The first thing we will do will be to clean up Havana, and not leave any place for fever germs to lurk," said Major Reed.

For a year and a half the most rigid sanitary measures were enforced. Deaths from other causes were reduced, but yellow fever went on its way unchecked. Plainly it was not a filth disease. Dr. Carlos Finlay, a physician in Cuba, offered the suggestion that the fever might be carried by the bite of a mosquito. The other members of the Commission scoffed at the idea.

"Everything else has failed in explaining why the disease spreads. I see no reason why we should scoff at this idea," remarked Dr. Reed. "It is certainly worth investigating."

There was but one way to find out, and that was for those who had not had the fever to be bitten by a mosquito that had come from the body of a yellow fever patient. The members of the Commission tried the experiment on themselves. Dr. Carroll was bitten by an infected mosquito, took the fever, and came near dying. Dr. Lazear allowed himself to be bitten by a mosquito, took the disease in its worst form, and died a martyr to the cause of science.

"It seems that we must try this experiment on a large scale, and build special houses for the purpose," said Dr. Reed to the Commission. "I am beginning to think the mosquito has much to do with it."

An experiment camp was therefore built, named "Camp Lazear" in honor of the dead doctor who had sacrificed his life in the cause of investigation. Two houses were erected. One was filled with infected clothing, soiled articles, bedding, and everything that could possibly spread the disease from one person to another. All mosquitoes were carefully excluded from this building. Nothing was left to carry the disease, but the clothing and bedding.

The other building was clean, airy, free from infected articles of any kind. But inside the screens were placed a number of mosquitoes that were known to be infected. Then came the call for volunteers. Dr. Reed addressed the soldiers:

"Men, I shall not detail anyone to enter these wards. I am asking for volunteers. Dr. Lazear has just died from the results of an experiment. It may mean death to some of you, but it may mean the saving of hundreds of thousands of others."

One by one the soldier boys volunteered, until Dr. Reed had enough for his purpose. He explained to them their danger and their duties. He then offered to each one a sum of money. "We take no money for this," they replied. "It is a condition of our going that we receive no pay."

"Gentlemen, I salute you in the name of humanity and your own great Government," said Dr. Reed.

For twenty days and nights, the men lived in their different quarters. In the clothes-infected house the men slept in the yellow fever beds, handled the clothing of patients, and breathed the air that had passed over infected articles. Not one of them took the fever.

In the other house, clean, sweet, airy, but full of mosquitoes, ten out of thirteen came down with the fever, but the cases were light and not one of them died.

The experiment proved conclusively that yellow fever was carried by the bite of a female mosquito, which had previously bitten a yellow fever patient. It was not carried by the clothing, and it did not infect the house. Its spread could be controlled by killing the mosquito, or by screening the sick-room.

Dr. Reed died shortly after he had announced the results of his investigations. In a letter to his wife, he wrote,

"The prayer that has been mine for twenty years, that I might be permitted in some way and at some time to do something to alleviate human suffering, has been granted."