At a disability rights meeting in Minnesota a while ago, some of the participants were worried about the ease with which an increasing number of courts are allowing parents or other relatives to remove feeding tubes and other life-sustaining treatment from patients in a persistent vegetative state or otherwise beyond communication.

A man with cerebral palsy said, "You can almost track which category of 'useless people' will be next. My bet is patients with Alzheimer's disease." There were no significant dissents.

I thought of that one afternoon while reading a recent article in the Journal of the American Medical Association. Each week the magazine has what could be called a quiet page -- no analyses of specific diseases and their treatment but rather a place where physicians can reflect philosophically on anything they choose.

This article, "Mercy Killing: Mercy for Whom?" by Dr. James S. Goodwin of Milwaukee began with a question: "Why do they shoot horses?" To put them out of their misery, he answered. And anyway, "with horses, there may be no alternative. A horse cannot live with a broken leg or only three legs."

But what about the "putting to sleep" of other animals? "Killing old, sick, injured or unwanted animals is common in our society," and the reason is that "we are relieving, or sometimes preventing, their misery."

However, Dr. Goodwin says, "Is there any evidence that sick animals want to die. ... I cannot find in the literature, or in folklore, suicide by animals in a hopeless situation."

And while there are human beings who commit suicide, "how many patients with chronic obstructive pulmonary disease, with cancer, with congestive heart failure actually kill themselves? The vast majority of these people not only do not want to die, they tolerate long, tedious, sometimes painful treatments in the frequently vain hope of prolonging their lives."

Then there are those patients who can no longer say whether they would prefer intense, invasive treatment rather than be killed. As mercy killings of the incompetent increase -- the family explains it cannot bear to see the patient suffer -- the question increasingly rises as to whether the family or the physician or society "have the right {or even the responsibility} to relieve suffering by killing the patient with Alzheimer's disease."

The corollary question, Dr. Goodwin adds, is: "Whose suffering is being relieved? In my years of caring for such patients, I have known few who were chronically miserable. My impression is that patients with Alzheimer's are no more or less happy than those with normal cognitive functioning. But the families suffer terribly."

Killing the patient is a merciful release for the family. But as for the patient, "We know nothing of the inner experience of the patient with Alzheimer's disease. The Alzheimer's patient, or the patient in a chronic vegetative state, or, for that matter an infant {born disabled}, assumes a vulnerability similar to that of horses: their loved ones, with the best of intentions, can put them to sleep to relieve their suffering, whether or not they want to die."

The killings are legal in those states -- and that's most of them -- which pretty much leaves it to the relatives and their physician to decide whether to end a life, even if the unresponding patient is not terminal.

Meanwhile, in some cases -- such as that of 17-year-old Christine Busalacchi in Missouri -- neurologists and other experts take sides. "There is no one there," one neurologist says. The other disagrees vigorously, citing evidence that Christine Busalacchi has waved her hand in response to a request and has made sounds to indicate which soap operas she wants to watch on television. The rebuttal is that these are muscle spasms, with no meaning. She is no longer capable, says the thumbs-down neurologist, of joy or thought.

This particular battle for life is taking place in the same Missouri Rehabilitation Center where Nancy Cruzan was being cared for until her feeding tube was taken away. Some say a slippery slope is already in evidence.

Jean Rostand, the French biologist, cautioned 20 years ago that "a terrible precedent would be established if we agreed that a life could be allowed to end because it was not worth preserving. ... The notion of biological unworthiness, even if carefully circumscribed at first, soon would become broader and less precise."

That's what the people at the disability rights meeting in Minnesota were saying with considerable apprehension.