On a gray February morning Troy Epps sits on his bed at LDS Hospital waiting for another treatment of Cis-platin. The chemical hovers in a bottle above his head and in a few minutes it will begin to drip slowly into his body. Then it will launch its offensive against the cancer cells in his lungs.

Like other members of the chemotherapy arsenal, Cis-platin is somewhat indiscriminate in these attacks, having trouble distinguishing between the cells that Troy's body wants to be rid of and those that need to stay. Hair is one of the hapless victims.For Troy, 16, the baldness is a grim reminder that his body is still at war.

But wait, here comes Karli George. George is a nurse on 8-East, and what she sees when she sees Troy's shiny, smooth head is a chance to have some fun.

"Let's do our hat trick," says George, reaching for Troy's gray wool fedora. "We've been practicing it all week," she explains to a visitor as Troy tries to position his head just right to snag the hat that is now sailing across the room.

"You should see him do his Freddy Krueger imitation," says George. Troy reminds her that he's making a Freddy glove so he can look even more like the villain from "A Nightmare on Elm Street." They both laugh as Troy pulls the hat at a slant over his eyes.

In Karli George's view of medicine and the universe, poking fun is just as essential as poking needles. Laughter, she knows, provides comic relief from the kind of anxiety that hangs heavy in the air in a place like 8-East.

Like a growing number of health professionals, George also thinks that humor may actually help in the healing process.

Laughter, in fact, may be the flip side of stress. The theory is this: If a stress such as the death of a spouse can negatively affect body chemicals - causing, for example, an increase in cortisol - and this in turn can cause the immune system to act sluggishly, perhaps leading to disease, then maybe a positive emotional state such as laughter can do just the opposite.

Strip away the part about the cortisol and it's a theory that is as old as the Bible, which counsels that "A merry heart doeth good like a medicine." What people have suspected instinctively for thousands of years, scientists are now investigating with sophisticated tools such as cell flow cytometry.

"We're really in the horse and buggy era with this research," cautions Dr. Lee Berk. Berk is an assistant professor at the Loma Linda University School of Medicine, where he does research into the immunology of both laughter and exercise. Preliminary studies indicate, he says, that laughter does cause a decrease in cortisol and other suspect chemicals, and therefore appears to boost the immune system.

Berk and his colleagues, including Dr. Robert Fry, a psychiatrist at the Stanford University Medical School, evoke laughter in the laboratory by showing their subjects a video of Gallagher, a comedian partial to pummeling watermelons with a "sledge-o-matic."

"We're not saying `Go out and laugh and get rid of your cancer,' " says Berk. "But we're saying that laughter can be part of a patient's own apothecary, if you will."

The researchers are planning more studies to determine, for example, whether it matters, immunologically, if you laugh a big belly laugh or a tiny giggle.

In a separate study, Fry determined that laughing 100 times a day - well within the range of the normal person's laugh potential, apparently - is equivalent to about 10 minutes of rowing. Laughter, he says, is like "stationary jogging."

Berk notes that the link between humor and healing, once considered sort of joke itself among serious doctor-types, is now getting mainstream attention. Laughter research is just one branch of the new field of psychoneuroimmunology, which studies the link between attitude and health. Scientists are looking into the effects of conditions once considered beside the point - the effect of optimism, for example, and family ties.

When it comes to a potentially stressful event, notes Patty Wooten, "It's not what's happening that's important; it's how you look at the event." That's why humor is so important, she says, because it puts situations into perspective. "It gives you a sense of the absurdity of things."

Wooten is an intensive care nurse in Alameda, Calif., and the originator of "Jest for the Health of It," a series of workshops aimed at preventing burn-out among health care professionals.

Wooten, Fry and Berk will be featured on a live satellite videoconference called "The Healing Power of Humor," which will air in Salt Lake City on Feb. 22 at LDS Hospital.

Also participating will be author Norman Cousins, who is credited with bringing national attention to the notion that it might actually be possible to laugh yourself well. In "Anatomy of an Illness," Cousins chronicled his use of massive doses of "Candid Camera" re-runs and vitamin C to cure him of a disease that was destroying the connective tissue in his spinal cord.

Since then, Cousins has joined the faculty of the UCLA School of Medicine, and a growing number of hospitals have begun trying to inject a little comedy into the least likely of situations. Some hospitals provide stand-up comics; others have "laughmobiles" full of funny videos and cartoon books.

Several Salt Lake hospitals are currently exploring setting up such programs. Meanwhile, at Holy Cross Hospital, bereavement counselor Kathleen Braza occasionally dresses as Daisy the Clown to bring a little lightness to the hospital staff and patients.

At LDS Hospital, nurse Karli George tries to laugh as much as she can with her patients. George knows that it can be a drag to be in the hospital: Shortly after moving from Oregon to Salt Lake City to take the position at LDS, George was hospitalized for diabetes.

"I know what it's like to be a patient. It taught me how important humor is when you're in a vulnerable situation."

George says that some of her patients don't respond to her jokes, but these are the ones who are very depressed. "You could walk in and do a stand-up act and a soft shoe and nothing would happen."

But with other patients the playful banter is non-stop. Ponie Reese, 64, was at LDS last year for chemotherapy and remembers, almost with fondness, his time there. After his final treatment he presented George and her colleagues with a trophy for being such good sports.

"You suffer enough," says Reese, remembering the heavy doses of chemicals and apprehension. "If you don't have something to laugh about, then your misery is worse."