Larry Davis propped his 6-foot 4-inch 200-pound frame on a gymnasium bench and wiped a tear from his eye. His 3-month-old kitten, Coltrane, had distemper and had to be hospitalized.

It was a touching display of affection, and one made more unusual by the fact that it occurred behind the barbed wire fences and red brick prison walls of the Lorton Reformatory in Fairfax County, where Davis is serving a 40-year sentence for rape, attempted murder, and armed robbery.

Prison officials say that Davis' cat is but one of about 800 cats roaming about the 5,000-acre institution, run by the District of Columbia. Lorton, it seems, is where many Washington area residents go to abandon unwanted kittens.

And to the surprise of humane society officials, the cat population in the sprawling prison is booming and remarkably healthy.

This weekend, officials from the Washington Humane Society, troubled by an inmate's complaint that the cats posed a health hazard both to inmates and other cats, went to Lorton to check the cats out.

What they found was as loving a group of cat lovers as was ever pictured in any "Morris the Cat" commercial.

When I want to stroke something I can stroke my cat," said inmate Davis as he coddled his cat. "He's a nice kitty."

The cats seem to permeate the prison, slipping from the crawl spaces under the gym to the rafters above the dining halls, unrestricted by the bars that confine Lorton's 1,100 inmates. Many of the cats were abandoned at a nearby landfill, but others are part of a hardy breed that has lived on the reformatory grounds for at least 10 years.

"I've been a guard here for 10 years," said Lt. E. F. Kennedy. "And the cats have always been here. They climb the fences, under them, and through small holes. The inmates love them, so they've decided to stick around."

As recently as four years ago, cats were captured and summarily exterminated, another guard said. "If we tried to do that now, we would have a riot on our hands," he said.

Inmates say the cats, many of whom are allowed to live with the prisoners inside the cellblocks, have improved morale tremendously.

"It's a sensitive thing with the guys. They take a lot of pride with the cats," said Jake, an inmate who said he has been in and out of Lorton since he was 16 years old.

"These are the guys you read about. Maybe they shot or knifed somebody. They're all "Mr. Tough Guy' with the other prisoners, but they'll sit and stroke a cat for hours. They are something we can love," Jake said.

Charles, serving up to 40 years on 1976 grand larceny and burglary convictions, said he built a house for his cat friend, Socks, out of wire and wood scraps.

"They kill roaches. We haven't seen a rat in months. They sleep beside you, keep you company. You can get along with the cats better than the inmates," Charles said.

Guards say inmates have faked illnesses with the prison doctor to get drugs that they can administer to the ailing cats. And prison guards concede they look the other way when a prisoner smuggles food from the dining hall to give to his cat.

In the same way that prisoners earn reputations in "Harlem Uptown," as the 125-inmate dormitories of Lorton's central facility are known, the prison cats are known for their idiosyncrasies.

"Charles the Molester" is an example. "He sneaks up on unsuspecting female kittens, and uh . . . well you know what he does," one inmate said. "He's a real cradle robber."

"When the cats have litters, some of the guys give them to inmates who don't have pets. It's the one pacifier these guys have," guard Kennedy said.

Jane Goldenberg, executive director of the Washington Humane Society, said the group became worried about the cats after an inmate wrote that a lack of proper medical attention for the cats might cause an epidemic among the feline population. The inmate's fears were unfounded, she said. What's more, she said the society found "no possibility" of the cats causing a health problem for the prisoners.

"We're giving the cats flea collars, rabies and distemper shots. We check for earmites and classify them," Goldenberg said.

The Humane Society plans to return to Lorton Thursday to round up any stray cats there. After that, Goldenberg said, the society plans to spay and neuter the remaining cats to control their numbers.

While some prison experts say it isn't unusual for prisoners to have an occasional pet, Goldenberg said she was surprised by the number at Lorton.

As a sweltering September sun bore down on the South Walk prison yard, several cats languished in the shade of the dormitories. But the sound of a bell was enough to shake them from their stupor.

"Every cat in this prison knows the sound of that lunch bell," a guard said. "The little devils are sure smart."