"What of soul was left, I wonder, when the kissing had to stop?"- Robert Browning, A Toccata of Galuppi's.
In a warm room just off Merrion Square, a guilty-looking man is placing a kiss on another's cheek. A motley flock of onlookers have gathered around the spectacle, nursing a strange mixture of curiosity and delight. Some even lean forward for a closer look.
Usually, in a circumstance such as this, one might steal a glance and turn away. It is not so often, after all, that one encounters two men sharing such an intimate gesture in public. But these men are different. The kiss they share is loaded and lingering, their faces are poised, and you get the feeling that once the kiss becomes unstuck, something incredible is going to happen.
Judas has been kissing Jesus like this for 398 years, ever since his glistening, bawdy face emerged from beneath the strokes of Caravaggio's brush. The Taking of Christ, perhaps the National Gallery's most significant painting, portrays one of the most fraught kisses in art. A lowly, dark and overtly real act, the kisser's lips are frozen in time, about to set in flow an irreversible and catastrophic chain of events.
As Judas's gesture of betrayal attests, however, a kiss is not such a simple thing. Defined in the Oxford English Dictionary as "a touch with the lips, especially as a sign of love, affection, greeting or reverence," the same physical marriage of lips can represent the first sweet sip of romance, or a surefire signal that the end is nigh. Less romantically perhaps, in verb form "to kiss" also denotes "the slight impact experienced when one snooker ball lightly touches another". Proof, as if it were needed, that kissing has a salad of meanings no other act of interpersonal contact can match, and no dictionary can master.
Scientists are continually surprised by just how meaningful kissing can be. Most recently, in a study conducted at Butler University, Indiana, researchers found couples recall up to 90 per cent of the details surrounding their first kiss. Working to throw light on our memories of significant life events, the team had expected loss of virginity to rank at number one. Instead, participants in the study prioritised both their first kiss, and the first kiss with their current partner.
What was it that inspired kissers to remember the kind and colour of the clothes they wore, the first words exchanged after their lips parted? Dr John Bohannon, who orchestrated the study, says the first kiss represented an "emotional gateway" between childhood and adult sexuality that not even sex could replicate. "You only do it once, it bears the weight of a mass of social mythology and, unlike first sex, it appears rarely to disappoint."
In The Devil's Dictionary (1911) Ambrose Bierce defined the noun as "a word invented by the poets as a rhyme for bliss." While not quite as cynical, the sum total of our physiological knowledge lacks equally in glamour. The Butler team, for example, knows the average kiss to last 45 seconds and involve 34 muscles. Biologists know that, during osculation, testosterone levels rise in both sexes, dopamine chases around the brain and adrenaline issues forth, increasing our blood pressure and raising our heartbeat. Our lips are extremely sensitive layers of tissue, charged as they are with capillaries and nerves. When we're aroused, the increase in blood flow causes them to swell a little.
Hence lipstick. Serving to accentuate the lips, to mark them out for distinction, lipstick invites eyes towards the wearer's mouth, raising the tantalising potential, perhaps, for a big fat snog. Marilyn Monroe's lips garnered much of their outrageousness from ritual dosing of bright red lipstick. The screen kisses of Bogart and Bergman, Hoffman and Bancroft and others would have been less memorable without the pouting colours. So too, would have been the longest kiss in mainstream cinema, Jane Wyman and Regis Toomey's 185-second marathon in You're in the Army Now (1941).
Chemists know that a kiss creates chemical changes in the amygdala, a part of the brain associated with strong emotions. They also know that the area of the brain concerned with the mouth is actually larger than that concerned with the genitalia.
Anthropologists know the kiss was first recorded as an expression of affection by Romans over 2,000 years ago, and that Eskimos and the Polynesian populations of many Pacific islands have survived without it. Philologists and archaeologists know, however, that Latin words and archaic pottery reveal kissing to be a far more ancient activity.
So did John Keats. Combining a basic lesson in anthropology with a graceful Biercean rhyme, Ode on a Grecian Urn (1820) can't quite decide whether it is a good thing or bad that the lovers are trapped in ceramic, stifled but immortal. "Bold Lover, never, never canst thou kiss / Though winning near the goal - yet, do not grieve; / She cannot fade, though thou hast not thy bliss, / For ever wilt thou love, and she be fair!"
Zoologists know that we're among the only species who do kiss, however luxuriously. Kissing serves no reproductive purpose, and indeed, sometimes transmits bugs that serve the opposite end. At first glance, kissing would seem to be the ideal conduit for germs - from influenza and the common cold to herpes (cold sores) and meningitis. In fact, the vast majority of bacteria in our mouths are either beneficial or harmless and some scientists suggest it may have been essential to our survival that we exchanged such bacteria in the first place.
Even flu is better transmitted through the air - inhaled rather than swallowed, landing in vulnerable lungs rather than powerful stomach acids.
Nevertheless, the Kiss of Death remains a timeless symbol of betrayal - an apparently friendly act that inevitably leads to ruin. Judas excelled at it. Poison Ivy relished in it. Georgie Porgy achieved it in a Freudian kind of way. In cinema too, most notably The Godfather, the Mafia makes use of the Kiss of Death. Subverting an archetypal gesture of love and turning it into a grisly portent of doom makes for particularly compelling viewing.
That kissing retains such importance in an age of seemingly unfettered promiscuity however, as the Butler survey demonstrates, reminds us more of the gesture's life-giving properties. Whether a kiss can still claim the power to transmogrify frogs into princes is debatable, but a million buxom kisses of life on Baywatch can't be wrong. Nor indeed, can babies - the most incessant kissers of all. Child psychologists and parents the world over know babies show a high awareness of their mouths and continually examine objects by bringing them to their lips. They know too, that children kiss instinctively, with little regard for social consequence.
Casanovas of the record books know better than to prophesise doom. The Guinness Book of Records documents the longest underwater kiss and the most kisses undertaken in an hour. Last April, Dror Orpaz and Karmit Tsubera kissed for 30 hours and 45 minutes in Tel Aviv. The kiss was a new world record, winning the couple a pair of round-the-world plane tickets and $2,500. "For nearly 31 hours they didn't eat, drink, talk or even go to the bathroom," a spokesperson for Colgate, the competition sponsors, said. "And the whole time, they were standing up."
The more you think about it, the more ubiquitous kissing seems. Princess Diana stole a kiss from her prince on the balcony at Westminster. The Pope's first act on Irish soil in 1979 was to kiss the concrete at Dublin Airport. A kiss awoke Snow White from eternal slumber; Anna Friel and Kerrie Taylor's embrace on Brookside had Channel 4 quaking in their boots when the time for rebroadcasting came. Eventually, the scene was cut from the Omnibus edition.
On the Internet we can now email digital kisses, have them worm their way through cyberspace, planting themselves on the far-off computer screens of our wayfaring friends and loved ones. New technology has not halted the progress of the most photographed, painted, filmed and fated gesture ever to have slipped our lips, a gesture as layered as a matryoshka doll.
Whether a kiss still has the power to usher in religions, transform frogs or shock TV audiences is open to argument, but one thing's for certain. Whether you're whistling beneath the Christmas mistletoe, openly defying cinematic code in the back rows of the Savoy or simply kissing your children goodnight, as long as there's humankind there'll be kissing. And this Valentine's Day, for every reason under the sun, retailers are forecasting a rash of it.
Do you remember the first time?