FUKUOKA, JAPAN -- "I could never again wear a white smock," says Dr. Toshio Tono, dressed in a white running jacket at his hospital and recalling events of 50 years ago. "It's because the prisoners thought that we were doctors, since they could see the white smocks, that they didn't struggle. They never dreamed they would be dissected."

The prisoners were eight American airmen, knocked out of the sky over southern Japan during the waning months of World War II, and then torn apart organ by organ while they were still alive.

What occurred here 50 years ago this month, at the anatomy department of Kyushu University, has been largely forgotten in Japan and is virtually unknown in the United States. American prisoners of war were subjected to horrific medical experiments. All of the prisoners died. Most of the physicians and assistants then did their best to hide the evidence of what they had done.

Fukuoka is midway between Hiroshima and Nagasaki, which are planning elaborate ceremonies to mark the devastation caused by the United States dropping the first atomic bombs. But neither Fukuoka nor the university plans to mark its own moment of infamy.

The gruesome experiments performed at the university were variations on research programs Japan conducted in territories it occupied during the war. In the most notorious of these efforts, the Japanese Imperial Army's Unit 731 killed thousands of Chinese and Russians held prisoner in Japanese-occupied Manchuria, in experiments to develop chemical and biological weapons.

Ken Yuasa, now a frail, 70-year-old physician in Tokyo, belonged to a military company stationed just south of Unit 731's base at Harbin, Manchuria. He recalls joining other doctors to watch as a prisoner was shot in the stomach, to give Japanese surgeons practice at extracting bullets.

While the victim was still alive, the doctors also practiced amputations.

"It wasn't just my experience," Dr. Yuasa says. "It was done everywhere."

Kyushu University stands out as the only site where Americans were incontrovertibly used in dissections and the only known site where experiments were done in Japan.

Today, the anatomy building at the university sits on a weedy lot, almost lost on an austere, modern campus of concrete and brick. No marker tells what the building is or what it was. A thick layer of dust covers the floors inside.

All memory of what occurred here in the waning days of the war might have decayed with the lab were it not for a small number of people who have kept its history alive.

One of them is Dr. Tono. As a medical assistant, he took part in several of the human vivisections, and he spent the 1960s and 1970s examining records and roaming the hills to piece together a full account. Against the advice of his colleagues, he published his findings in a book he entitled "Disgrace."

"Doctors asked me, 'Why did you have to disclose it?' " Dr. Tono says now. "You weren't supposed to admit what happened during the war."

On May 5, 1945, an American B-29 bomber was flying with a dozen other aircraft after bombing Tachiarai Air Base in southwestern Japan and beginning the return flight to the island fortress of Guam.

Kinzou Kasuya, a 19-year-old Japanese pilot flying one of the Japanese fighters in pursuit of the Americans, rammed his aircraft into the fuselage of the B-29, destroying both planes.

No one knows for certain how many Americans were in the B-29; its crew had been hastily assembled on Gaum.

But villagers in Japan who witnessed the collision in the air saw about a dozen parachutes blossom.

One of the Americans died when the cords of his parachute were severed by another Japanese plane. A second was alive when he reached the ground. He shot all but his last bullet at the villagers coming toward him, then used the last on himself.

Two others were quickly stabbed or shot to death, according to Toshio Kai, a high school teacher who has spent years following up the leads in Dr. Tono's book.

At least nine were taken into custody.

B-29 crews were despised for the grim results of their raids. So some of the captives were beaten.

The local authorities assumed that the most knowledgeable was the captain, Marvin S. Watkins. He was sent to Tokyo for interrogation, where he would be tortured but would nonetheless survive the war.

The doctor and the colonel

Every available account asserts that a military physician and a colonel in a local regiment were the two key figures in what happened next. What happened can not be easily explained. Perhaps caring for the Americans was an impossible burden, especially since some were injured. Perhaps food was scarce.

Whatever the reason, the colonel and doctor decided to make the prisoners available for medical experiments, and Kyushu University became a willing participant.

Teddy J. Ponczka was the first to be handed over to the doctors and their assistants. He had already been stabbed, in either his right shoulder or his chest. According to Dr. Tono, the American assumed he was about to be treated for the wound when he was taken to an operating room.

But the incision went far deeper. A doctor wanted to test surgery's effects on the respiratory system, so one lung was removed. The wound was stiched closed.

How Teddy Ponczka died is in dispute. According to U.S. military records, he was anesthetized during the operation, and then the gas mask was removed from his face. A surgeon, Taro Torisu, reopened the incision and reached into Ponczka's chest. In the bland words of the military report, Torisu "stopped the heart action."

Dr. Tono remembers events differently. The first experiment was followed by a second, he says. Ponczka was given intravenous injections of sea water, to determine if sea water could be used as a substitute for sterile saline solution, used to increase blood volume in the wounded or those in shock. Dr. Tono held the

bottle of sea water. He says Ponczka bled to death.

Then it was the turn of the other Americans.

The Japanese wanted to learn whether a patient could survive the partial loss of his liver. They wanted to learn if epilepsy could be controlled by removing part of the brain. There were further intravenous injections of sea water, and every time the result was the same. All the Americans died.

"There was no debate among the doctors about whether to do the operations -- that is what made it so strange," Dr. Tono says. It was, he says, the mood of the times.

The remains of the soldiers were at first preserved in formaldehyde, the better to be studied by anatomy students. There were second thoughts when Japan surrendered to the United States in August 1945.