Lucille Green, a 93-year-old resident of Bay Manor Nursing Home near here, sat in her dimly lit room with three other women. They waited without talking for the minutes to edge into lunch time.

Green's eyelids were closed. But when Tristan, a 5-year-old beagle with warm brown eyes, padded into the room, Lucille Green came to life: She lifted her head, smiled and stretched out her crippled hand to gently stroke the dog.

"I grin every time I see him," she said.

For Green and her roommates, Tristan was a friendly face and a break in the day. But for nursing home administrators, such pets have also become increasingly popular weapons in battling dementia, a progressive intellectual decline, commonly called senility, that strikes about 10 percent of people over age 65.

In recent years, pet therapy has been widely received in nursing homes and other long-term-care facilities across the country. Nurses and counselors say patients' mood, enjoyment and alertness improve when they are holding animals, but the scientific community was not convinced.

But Dr. Paul S. Rhodes, a Crofton geriatrician and internist who is on the staff of two nursing homes, concluded in a recent study conducted at Crofton Convalescent Center that playing with pets does help patients suffering from dementia. He will present a report on his findings this week at the Gerontological Society of America's 37th annual conference in San Antonio.

Rhodes and Anne Arundel County's director of aging, Nita Maggio, will also make presentations on the Anne Arundel "Pets on Wheels" program as a national model for pet therapy.

"The scientific community looks very carefully, tends to be very cynical about any claims about the effectiveness of pet therapy," Rhodes said, noting that such programs' value until now has been reported only in newspapers and popular magazines. "We've done this work with the hope . . . that it will be accepted by the scientific community."

Advocates of pet therapy hope the study will lead beyond recognition to public funding of what has been considered just a "cute program."

Rhodes -- along with a clinical psychologist, a Baltimore physician and a geriatric nurse -- conducted the study for six weeks, beginning in March 1983. He selected two groups of 15 from residents of the Crofton nursing home. The groups were of similar age and disability. One group was visited three times a week for 30 minutes a day by volunteers from Anne Arundel Community College; the other group was visited by the same volunteers bearing kittens.

Nurses' evaluations, videotapes, psychological interviews and the volunteers' analysis indicated that patients who played with the kittens, unlike the control group, showed "decreased signs of psychotic behavior," Rhodes said.

"We had one patient . . . who would never speak. He was suffering from dementia and depression, but he showed great enjoyment with pet therapy. He would show his cat off to the lady next to him," Rhodes said. "One time, when the kittens were playing on the floor, he shouted, 'They're fighting!' It's the first time we heard him talk."

Patients in the study seemed to improve in mood and alertness and seemed to relate better to the volunteers while they were playing with or observing the kittens, Rhodes said.

Most of the improvements were short-term, not lasting beyond the time the kittens were there, he said, but "the short term is most important in patients for whom the here and now is all that exists."

Volunteers said they, too, enjoyed their time with patients more with the pets present, perhaps explaining why the "Pets on Wheels" program reportedly has no trouble getting and keeping volunteers, unlike some volunteer programs.

Anne Arundel's program has enough volunteers to provide a pet a day to 10 of the county's 11 nursing homes. Only one home has declined to participate in the program, said Jeane Miller, program director. Approximately 1,250 residents of the 10 homes are reached.

Rhodes said he selected the Anne Arundel County program to exhibit at the conference in conjunction with his report because of its volunteer training program and because it is well organized and operates countywide under the auspices of county government.

Anne Arundel and Baltimore City were the first jurisdictions in Maryland to offer pet therapy. Anne Arundel began a six-month pilot program in July 1982 that was so popular that it was established as a regular program in March 1983 under the county's Department of Aging.

Although operated by the county, it receives no government money and relies on a recently established advisory board for fund-raising, Miller said. The program has 65 volunteers, who bring 77 dogs and cats. Any pet, from a hamster to the large, furry Burmese Mountain Dog, is considered suitable.

Volunteers are required to attend a two-hour training session on dealing with the residents and have in-service training sessions. The animals must be in good health, immunized and of even temperament.

Miller and her volunteers said they had no doubts about what Rhodes would find in his study.

"The whole atmosphere in a facility changes when you bring in an animal," Miller said. "A dog is nonthreatening. The dog doesn't care if people have no legs, if their teeth are gone."