Steve Wilson, a medical researcher, is driving an electrode deep into the brain of a living dog.

His Howard University laboratory, arrayed with beeping, blinking instruments to record the animal's vital signs, is as dark as the bridge of a ship. Classical music plays softly. Wilson is attempting, with a microscopic electrode of drawn glass, to penetrate a single cell in the caudate nucleus sector of the brain.

The dog, a beagle, lies immobile on a wooden operating table, its body shrouded in a green surgical sheet. Its head, to which wires are attached, is clamped upright in a metal frame. The brown ears hang limp, the mouth grips a plastic tube coiling from a tank of anesthetic.

A portion of the dog's skull is laid bare, disclosing a hole drilled to admit the electrode, which Wilson lowers from above by a mechanism resembling a drill press.

The beagle, purchased for $250 from a breeder in the Midwest, has no name, only the designation "BQB4" tattooed under an ear. Later, the experiment completed, BQB4 will be put to death. Wilson will administer an overdose of barbiturates, then profuse the dog's system with fixative to lock the brain, as if in cement, so it can be removed and studied.

Now, like the commander of a submarine maneuvering by instruments, Wilson advances the electrode through the murk of the inner brain. Green waves wash across his computer screens. A thrumming from the electrode tip reverberates from a speaker.

Suddenly, an increasingly loud thumping.

"That's heartbeat," Wilson says apprehensively. "See, it's getting worse. I think we're getting close to an artery right now . . . Shoot! . . . It's contamination."

He pushes past the obstacle, the beating sound fades. Then, low at first, a rising muffled roar like the ocean.

"It's a cell," Wilson says softly. "We're getting close to one . . . Now I've got to see if I can stick it."

The cells of the caudate, in ways not understood, modify neural signals that affect motor control.

Intent now, Wilson leans forward, fingers fluttering over instruments. He speaks into a recorder: "Uhhh, we're close to a cell now. I don't know what its resting potential is . . . We'll go ahead and take it."

The electrode tip enters the cell, stops.

The cell is 15/1,000ths of a millimeter in diameter, sk,2 sw,-2 ld,10 the electrode tip 1/50th that. So delicate is the penetration that a footstep in the lab could dislodge it.

Wilson tries to maintain the penetration while electrically stimulating other areas of the brain, prompting them to send signals to the caudate. The electrode records the cell's reactions.

"Okay.CX2 an area being stimulated . . . Losing the cell! . . . Do it again. There we go . . . Do it one more time . . .Almost have it . . . Possibly a little something . . . CX3!"

Few issues stir the emotions more than vivisection. This work, according to Wilson and thousands of other scientists, is absolutely vital if they are to find treatments for cancer, stroke, AIDS and other major diseases. Surveys have shown that Americans generally support this effort, though they may worry that researchers sometimes cause unnecessary pain and kill too many animals.

Members of the growing animal rights movement assert that it is immoral to cause pain or death to any sentient being, no matter how worthwhile the goal. These animal advocates -- some of them dressed in monkey costumes -- organized a motorcade two weeks ago to the National Institutes of Health in Bethesda, where they demanded the release of 15 research monkeys.

At least 200 members of Congress, led by Rep. Robert C. Smith (R-N.H.)., have signed a letter urging NIH to release the monkeys, seized by police at a Silver Spring lab in 1981 after charges of cruelty to animals. Smith says he will introduce a resolution in Congress this week for the monkeys' release.

For Wilson, a tall, bearded, soft-spoken man of 35 who does his research under an NIH grant, such protests are understandable "emotionally" but removed from the daily reality of his lab -- a grim struggle against human suffering.

Raised near military posts where his father was stationed, Wilson received a PhD in anatomy from the Medical College of Virginia in 1978, then did postdoctoral work at UCLA. There he became fascinated with what remains his research interest -- the cause and possible cure of Parkinson's disease.

"I've always been an animal lover," he says. "Growing up, I had dogs and cats and birds." Now he becomes close with experimental animals. "It doesn't take very long to get an attachment to them. You have to weigh them, you have to see that they're healthy. If you're around a dog for 15 minutes, if you like dogs as I do, you become very friendly."

After injecting a dog with drugs to induce the tremors and slow movements of Parkinson's, Wilson monitors it for a week in "a nurse-patient relationship." Then he conducts the electrode experiment and the final "sacrifice" -- researcher jargon for killing.

"You don't feel good," he says of the killing, "but you don't dwell on it. You go in and you sacrifice the animal . . . as cleanly and as quickly as you can." He must dissect the brain, he says, to determine precisely where the electrodes recorded data.

Wilson lives in a suburban house with his wife, who is a dentist, and their daughter. They have no pets, though Wilson and his daughter recently found a wounded bird, which they nursed to health and returned to its owner. At parties, the scientist -- who teaches anatomy classes as a professor at Howard -- has endured jokes about vivisection. In private moments, he has felt a certain heartache about his work.

"For me, it's the most unattractive part of the job that you have to work on animals," he says. "When I first started graduate research and had to do animal experiments, there was a period when I stayed up late at night trying to decide whether I'd stay in medicine. Even now -- do I really want to continue doing this? I have my karma to worry about, too, you know -- my soul."

Yet he has resolved to continue.

"There really isn't any other solution if you want to improve the health of people and their possibility of leading normal lives," he says. "If I can help contribute to the cure of Parkinson's disease . . . my life will have a positive impact on, you know, in this generation, a million people."

Wilson's work is part of a rebirth in Parkinson's research following the accidental discovery a few years ago of a "designer drug" -- called MPTP -- that produced Parkinson's symptoms in addicts. The discovery enabled researchers to create "animal models" for study by injecting them with MPTP.

"When I started in the field in the 1960s, there was no good way to make a model of Parkinson's disease," says Dr. Roger C. Duvoisin of Rutgers Medical School, a leading authority on the disease. He endorses Wilson's work, saying that L-Dopa, a drug used on Parkinson's patients, "has limitations and side effects and does not stop the underlying disease. Our patients need something much better."

Sidney Dorros, 60, a Gaithersburg resident and author of the Warner paperback "Parkinson's: A Patient's View," says that without animal research "I'd be dead by now."

Each year, 17 million to 22 million animals are used in laboratory experiments in the United States. Most are mice and rats. Agriculture Department figures show that in 1983 at least 182,000 of them were dogs, 55,000 cats, 59,000 monkeys, 454,000 hamsters, 521,000 guinea pigs and 509,000 rabbits.

The Animal Welfare Act of 1966, which Congress strengthened last year, regulates feeding and care of all of these except the rodents. At Howard and most institutions, the law requires committees of veterinarians, community members and others to ensure humane treatment.

"We look at every research proposal to see if animals are necessary," says William L. West, chairman of Howard's Department of Pharmacology and Toxicology and head of the university's animal care committee. "We find out if it can be done by alternative means. If animals are used, we see that everything is done according to the new laws."

For animal rights advocates, safeguards are not enough. They want the experiments ended.

On "National Laboratory Animals Day" in April, 139 protesters in nine states were arrested, some carrying "Animal Auschwitz" signs. People for the Ethical Treatment of Animals (PETA), which organized the motorcade to NIH, and other groups seek legal standing to sue for custody of the animals on grounds that -- among other things -- group members achieved personal "bonding" relationships with the primates.

Ingrid Newkirk, a PETA director, says the animal rights movement represents "the single largest group of exploited individuals on the face of the earth, and that is everyone who doesn't happen to have been born a human being . . . It's immoral to use any individual who can feel pain . . . whether that's your child . . . a prisoner of war, a dog, a monkey or a mouse."

Antivivisectionists first emerged as an organized movement in the mid-1870s in England, according to Richard D. French in the Encyclopedia of Bioethics. Today's "struggle for animal liberation," writes Peter Singer in "In Defense of Animals," " . . . marks an expansion of our moral horizons beyond our own species."

Newkirk, who was once arrested while protesting in a bird costume, said in a 1983 interview: "Six million people died in concentration camps, but 6 billion broiler chickens will die this year in slaughterhouses." Of Wilson she says, "Many people in experimentation don't see anything when they look into the eyes of an animal. They are not the type of people who emote well."

Martin L. Stephens of the Humane Society of the United States says the society seeks an eventual end to animal research, the benefits of which are "overrated . . . There's wastefulness, unnecessary duplication . . . the pressure to do research and to publish." As alternatives, he suggests research in cell cultures and human volunteers.

Wilson and other scientists say that experiments on human volunteers are strictly circumscribed by ethical considerations. Cell culture research, they say, yields important but limited results -- and most of those cells come from living animals anyway.

"If the animal rights people have their children vaccinated against polio then they must be hypocrites, because they know how many monkeys had to perish in order to develop the vaccine," says Nobel Prize-winning Dr. David H. Hubel of Harvard University. His vision experiments in cats and monkeys have aided the treatment of cross-eyed children.

Polio, AIDS, diabetes, cancer, heart disease, stroke, diseased organs, diphtheria, smallpox, hepatitis, Alzheimer's disease, multiple sclerosis and damage to the central nervous system are among disorders that have been studied in animals. Of the 52 Nobel winners in medicine in the two decades prior to 1984, 37 conducted experiments on live vertebrates.

"Virtually every medical innovation of the last century . . . has been based to a significant extent upon the results of animal experimentation," according to William Raub, who oversees 20,000 NIH biomedical research grants worth $4 billion annually. "Biomedical research would be set back into the Dark Ages if we weren't permitted to continue," says Dr. John C. Rose, vice chancellor of Georgetown University Medical Center.

A recent 441-page report by Congress' Office of Technology Assessment, "Alternatives to Animal Use in Research, Testing and Education," concludes: "Some biological research requires -- and in the foreseeable future will continue to require -- the use of live animals." The reports adds that "researchers can attempt to reduce the number used and also to minimize pain and distress."

In April, organizations including the American Diabetes Association, the Arthritis Foundation and the National Kidney Foundation held a sparsely attended press conference to support animal research.

A representative of the Huntington's Disease Foundation said: "You won't find people decrying the use of animals in biomedical research who have parents whose every waking moment is plagued by uncontrollable twisting, writhing and flailing, and whose powers of reason, memory and judgment are fading away."

Huntington's disease is hereditary.

Wilson, who uses about a dozen dogs a year and publishes the results of his experiments in scientific journals, has a $90,000 NIH grant. NIH's Raub says one in four grant applications is funded, and that Wilson's work "has been reviewed and rated highly in national competition . . . There's no question whatsoever on a project like that about its relevance to human health."

In 1982, when Wilson had been at Howard a year and had not yet set up his costly lab, an underground group called the Animal Liberation Front broke into the medical school, causing thousands of dollars in damage and stealing several dozen research cats. One of his colleagues studying peripheral nerve injuries in cats, Wilson says, "lost a year's worth of research."

"They're starting to have a very negative impact," he says of the animal rights activists. "You begin to question whether or not you want to continue doing research on larger animals, and I'm very seriously thinking of doing what is called 'safe science' -- science which doesn't upset anybody."

Having allowed a reporter into his lab, Wilson plans to "take precautions, so I won't have to worry."

"He should be worried," says PETA's Newkirk, adding that "we speak for" the Animal Liberation Front. "What he does isn't probably very attractive . . . No one knows what they the Front are going to do. We learn after the fact. But they rescue lots of animals, who thank them very much."

"We're peaceful people," she says. "We're against causing pain or suffering to any living creature, including him Wilson . But the thing is, if he uses animals, he causes them discomfort at the very least . . . If he's really worried, it would benefit us all if he'd go grow a soybean."

Animal liberation, Wilson says, "emotionally sounds very nice." But he thinks it is "very stressful to the animals . . . When somebody breaks in, they have no idea of what experiments have been done on those animals . . . If they're hooked up to any monitors, for instance, the removal of those monitors has to be done very carefully."

Beyond this, he says, liberation can be dangerous. "Some of these animals do contain neurotoxins, or they may contain infectious agents or . . . they're injected with an AIDS virus. And when you remove them from a controlled environment and put them out in the community, what are they exposing the community to?"

The MPTP Wilson uses on dogs, he says, is a neurotoxin so dangerous that touching or inhaling traces of it could destroy brain cells and induce Parkinson's symptoms. He says he takes elaborate precautions with it, avoiding the feces and saliva of MPTP-injected dogs.

Finally, Wilson says, animal liberation is "illegal. If you liberate a monkey, for instance, that's over $1,000 of initial cost, not counting what's been invested in him afterward. That's plain grand larceny."

West, Howard's animal care committee chairman, thinks authorities don't deal firmly enough with liberationists. "Administrators are afraid because it may be children whose parents are contributing heavily to the university," he says. "So they get away with murder."

Most scientists have avoided stepping forward to publicly support animal research. Wilson says he did so because he has "no apologies. I think it's something that should be discussed. The use of animals is not my decision . . . It's the decision that society makes.

"You just can't be intimidated by fanatics."

Why, of all animals, beagles?

"The reason I'm doing dogs is the Parkinson's syndrome looks very similar to what you see in humans," Wilson says. "And they're cheap. Monkeys cost $1,500."

He uses "the lowest species possible" for each experiment to decrease the number of variables he must contend with. Monkeys, the next step up from dogs, are more complex.

"If I could do all the experiments in rats," he says, "I would do them."

But beagles?

"That's what the NIH was using, so I could draw on their data," he says. "I wouldn't have to repeat any of their experiments."

Dr. Irwin J. Kopin, director of neurological research at NIH, says, "Beagles are purebred, so they're consistent from one animal to another. If you're doing experiments, you want consistency." He says Parkinson's researchers at NIH first "tried rats, and it didn't work in rats. We wasted two years trying to use small animals."

An added attraction of beagles, Wilson says, is that "after a period of time, they show a significant recovery to the Parkinson's syndrome. That's one of the most interesting things. If we can figure out how the dog recovers, maybe we can learn how a human could recover."

Wilson says his dogs experience no pain, that the MPTP even puts them into a drugged "high" for a time. "They're not suffering," he says. "We do everything we can to reduce any possible stress."

The NIH's Raub says most scientists treat animals well: "You can't do good science without good animal care."

Nevertheless, much animal experimentation involves pain. A pamphlet of the Foundation for Biomedical Research says that in 6 percent of experiments "anesthesia and pain-killers must be withheld because they would obscure the results of the research. An example . . . is the study of pain, itself a major human health problem."

"Pain," says Nobel winner Hubel, "is one of the most awful things there is. If you're going to study it, you could imagine that the only way to do it is with animals, but then it's incumbent to minimize the pain . . . I admit that there are two sides to the question."

For Wilson, the question of pain, of experimenting on animals at all, is constantly in mind as he balances the good he may do for people against his sympathies for animals.

"Emotionally," he says of the animal rights advocates, "I agree with them. You know, what right does anybody have to take any life whatsoever? I respect somebody who says that and then lives according to those rules . . . What I don't like is them imposing their moral decision on other people . . .

"Who's going to be hurt if animal research is stopped? Well, just think for a minute. It'd be Parkinson's patients."