And so, against the advice of her doctors, the patient decided to stop eating and drinking.

During the next 40 days in 1993, Robert Sullivan of Duke University Medical Center observed her gradual decline, providing one of the most detailed clinical accounts of starvation and dehydration.

Instead of feeling pain, the patient experienced the characteristic sense of euphoria that accompanies a complete lack of food and water. She was cogent for weeks, chatting with her caregivers in the nursing home and writing letters to family and friends. As her organs finally failed, she slipped painlessly into a coma and died.

In the evolving saga of Terri Schiavo, the prospect of the 41-year-old Florida woman suffering a slow and painful death from starvation has been a galvanizing force.

But medical experts say going without food and water in the last days and weeks of life is as natural as death itself. The body is equipped with its own resources to adjust to death, they say.

In fact, eating and drinking during severe illness can be painful because of the demands it places on weakened organs.

''What my patients have told me over the last 25 years is that when they stop eating and drinking, there's nothing unpleasant about it - in fact, it can be quite blissful and euphoric,'' said Perry Fine, vice president of medical affairs at the National Hospice and Palliative Care Organization in Arlington, Va. ''It's a very smooth, graceful and elegant way to go.''

Schiavo, who hasn't had any food or water since March 18, has been in a persistent vegetative state for 15 years that makes it impossible for her brain to recognize pain, doctors say.

''Her reflexes with respect to thirst or hunger are as broken as her ability to think thoughts or dream dreams or do anything a normal, healthy brain does,'' Fine said.

But even if her brain were functioning normally and she were aware of her condition, she would be comfortable, doctors say.

''The word 'starve' is so emotionally loaded,'' Fine said. ''People equate that with the hunger pains they feel or the thirst they feel after a long, hot day of hiking. To jump from that to a person who has an end-stage illness is a gigantic leap.''

Contrary to the visceral fears of humans, death by starvation is the norm in nature - and the body is prepared for it.

''The cessation of eating and drinking is the dominant way that mammals die,'' said Ira Byock, director of palliative medicine at Dartmouth Hitchcock Medical Center in New Hampshire. ''It is a very gentle way that nature has provided for animals to leave this life.''

In a 2003 study published in the New England Journal of Medicine, 102 hospice nurses caring for terminally ill patients who refused food and drink described their patients' final days as peaceful, with less pain and suffering than those who had elected to die through physician-assisted suicide.

After 24 hours without any food, ''the body goes into a different mode and you're not hungry anymore,'' Sullivan of Duke University said.