THE MOST INTIMATE BOND

IT'S PLAY PERIOD IN Connie Stahlke's kindergarten room. Abigail and Brittany Hensel are at the Play-Doh table, when a visitor asks, How much is 10 plus 10? Britty starts counting on her fingers. Abby helpfully lays down her hand on the table. They count fingers and toes with all the accuracy their six-year-old minds can muster. "Nineteen," they conclude. Then the clearly ancient guest asks, "Guess how old I am." Britty can't resist the chance to tease: "900,000!" she shrieks. The sisters dissolve into giggles. They reach up and slap a celebratory high five.

The Hensel twins love to share a joke. A puckish sense of humor is one of their best tools for contending with all the other sharing they must do day in and day out--a sharing of a more profound and intimate nature than most of us can imagine. The two hands that meet in a high five, offer fingers for counting and clasp their adored parents in an embrace belong to a single body. Abby controls the right limbs, Britty the left. Although they have separate necks and heads, separate hearts, stomachs and spinal cords, they share a bloodstream and all organs below the waist. In medical terms, they are known as "conjoined twins." In human terms, though, they are two very different people, with separate opinions, tastes and dreams.

For six years the Hensel twins have lived a quiet existence in a tiny Midwestern town where everyone knows them. (The family does not want the town to be identified.) They go shopping with their parents and younger brother and sister, attend school and even play in Little League T-ball games. But until recently when their parents opened their doors and hearts to a Life magazine reporter and photographer, the twins have been shielded from media attention. Their touching story, which appears on the cover of Life's April issue, has made them instant celebrities.

But the girls are more than curiosities. Their smiling faces and apparent good health seem a rebuke to the current medical trend of trying to separate, via surgery, ever more complexly conjoined twins--a trend that often means sacrificing one child so the other can live "normally." And their tale of lives unpunctuated by solitude has much to teach all of us about the real meaning of individuality and the limitless power of human cooperation.

Conjoined twins are a rare event in the world's delivery rooms. They occur about once in every 50,000 births, but 40% are stillborn, and, curiously, 70% are female. Conjoined twins are always identical: the product of a single egg that for some unknown reason failed to divide fully into separate twins during the first three weeks of gestation. In the U.S. there are perhaps 40 live cases each year; ordinary identical twins are 400 times as common.

The popular term Siamese twins originated with a celebrated pair named Eng and Chang, born in Siam (Thailand today) and exhibited across the U.S. from 1829 to 1840. Eng and Chang, who lived to the ripe old age of 63--still a record for conjoined twins--were connected at the chest by a flexible band of cartilage. (Modern surgeons could have separated them easily.) Connections at the chest and abdomen are the most frequent configuration for conjoined twins, though medical texts list more than a dozen possible permutations. Dicephalic twins like the Hensels, who have two heads but share one two-legged body, are among the rarest. Only three or four cases are on record.

Patty and Mike Hensel had no idea what they were in for when Patty's first pregnancy came to term six years ago. A spunky, attractive emergency-room nurse, Patty, now 37, had no signs that there was anything unusual about her pregnancy. Ultrasound tests indicated a single, normal fetus. (Doctors later guessed that the girls' heads must have been aligned during the sonogram.) Mike, who works as a landscaper and carpenter, thought he had heard two heartbeats at one point, but that impression was soon dismissed.

Because the fetus appeared to be in a buttocks-first, or breech position, Patty was scheduled for a Caesarean section. She was woozy with anesthesia, and Mike was not in the room, when doctors attempted the delivery. They pulled out the buttocks, then the legs and finally, to their astonishment, two heads. "We all stood in silence for about 30 seconds," recalls Dr. Joy Westerdahl, the family's physician, who assisted at the birth. "It was extremely silent."

Mike recalls the painful way he was given the news. "They had a pretty crude way of telling me. They said, 'They've got one body and two heads.'" Patty, still under sedation, heard the word Siamese and couldn't quite grasp it. "I had cats?" she asked.

The girls were whisked off to a children's hospital in a nearby city. "We thought they were going to die," recalls Patty, who remained bedridden in the community hospital where she works, suffering from dangerously high blood pressure. Her sister, Sandy Fiecke, acted as her surrogate for several days at the children's hospital. She held the tiny girls for hours, offered them bottles and wore Patty's or Mike's sweatshirts so the girls would come to know their parents' scents. The task of informing friends and family fell to Mike. "It's pretty hard to explain to your folks how the kids were put together."

But once it was clear that the twins were healthy and the family could fall into a normal routine of bathing, feeding and cuddling, "we knew it would be fine," recalls Patty. And so it has been. Aside from an operation at four months to remove a third arm that projected awkwardly between their heads, the girls have not needed surgery. They have been hospitalized briefly three times: twice for pneumonia in Britty's lung and once for a kidney infection.

Westerdahl says it is impossible to guess about their long-term prognosis but for now they are "healthy and stable." Brittany is more prone to colds and coughs than Abigail. Since their circulation is linked, notes Patty, "we know that if Abby takes the medicine, Britty's ear infection will go away." The twins need only one set of vaccinations, says Westerdahl: "They like that they don't have to get two shots!"

Though they share many organs, including a single large liver, a bladder, intestines and a reproductive tract, their nervous systems are distinct. Tickle Abby on her side anywhere from head to toe, and Britty can't feel it--except along a narrow region on their back where they seem to share sensation. The girls experience separate hungers and separate urges to urinate and sleep.

The fact that they learned to walk at 15 months seems a miracle of determination, encouragement and teamwork. "We praised them so much," remembers Nancy Oltrogge, the twins' day-care provider, who presided over the process. No one ever instructed the girls about who should move which foot when. "They knew what to do," marvels Oltrogge. "We just had to make sure we watched them because they were a little bit top-heavy and could tip over." Occasionally, though, the twins would disagree on which way to go. "All of a sudden," says Oltrogge, "they're going in circles." The twins have graduated to swimming and riding a bike.

No one can say how two separate brains can synchronize such complex motions. It is possible that the girls have developed an unconscious awareness of the placement each other's limbs. "How do they coordinate upper-body motion like clapping hands?" asks Westerdahl. "I don't know if we can ever answer that."

The idea of separating the twins was dismissed by both parents right from the start, when doctors said there was little chance that both could survive the procedure. "How could you pick between the two?" asks Mike. Even if separation were possible, Patty, as a nurse, could picture all too vividly a pathway of pain, multiple surgeries and lives spent mostly in wheelchairs. "If they were separated, they would pretty much cut them right down the middle. You can see that," she says.

This view is supported by Dr. Benjamin Carson, chief of pediatric neurosurgery at Johns Hopkins Children's Center in Baltimore, Maryland, who has helped separate other twins. "If we were to separate them, we would basically take a couple of individuals who are mobile and change them into invalids." He doubts that both could survive.

Perhaps the closest case in which separation was attempted is that of Eilish and Katie Holton of Ireland. Born in a configuration similar to the Hensels' but with four arms rather than three, the Holton twins were separated in 1992 at age 3 in a 15-hour operation involving 25 doctors at London's Great Ormond Street Children's Hospital. Katie died of heart problems four days later. Eilish survives and hobbles around quite nimbly with an artificial leg. Eilish and her parents visited the Hensels in December 1994. For each family, the visit, recorded for ABC's 20/20, was a stunning encounter with the road not traveled.

Patty and Mike worry about what will happen when the girls enter adolescence. "It's going to be tough on them," Mike suspects. Should there come a point where the girls insist on being separated, says Carson, the possibility could be explored, though conjoined twins have never been successfully divided after early childhood. "They would have to say, 'We can't stand this anymore.'" Aside from the physical difficulty, such a separation, he says, would present a "major emotional trauma."

Right now the girls seem content with their lot. "I'm not going to be separated," Britty insists. (Having met just one Holton twin, she has some sense of the risks.) Each girl seems to have established a remarkably solid sense of self. "They do their own work," says Stahlke, their teacher. "When we take tests, they could copy each other so easily, but they don't. If Abby makes a mistake, Britty has that one right. It just amazes me."

Abby wants to be a dentist. Britty dreams of piloting planes. "It's gonna be kind of hard in the cockpit when one's flying and the other one's working on someone's teeth," jokes Mike. They are already asking if they might someday find husbands. And why not? says Mike. Other conjoined twins have married. "They're good-looking girls. They're witty. They've got everything going for them, except," he pauses, "they're together."