(AP) - Some 150 years ago, a congressman from South Carolina, angered by a speech on slavery, entered the Senate chamber and beat a senator from Massachusetts into unconsciousness with a metal-topped wooden cane.
Years earlier on the House floor, a representative from Vermont attacked a colleague from Connecticut - also with a cane - only to be attacked himself with a pair of fireplace tongs.
And then there was the 1838 pistol duel in which William Graves of Kentucky shot and killed fellow congressman Jonathan Cilley of Maine over words spoken on the House floor. (He wasn't even expelled.)
Given those breaches of congressional protocol, it would seem that a mere shout of "You lie!" from a 21st-century South Carolina congressman would be small potatoes. Especially when compared with a global tradition of brawls, scuffles, hurled insults (sometimes fruit, too) and other mayhem in legislatures around the world.
Yet there's little if any historical precedent for a U.S. congressman individually challenging a president during a speech to Congress - let alone accusing him of lying - which is just one reason why some longtime political observers were stunned by Rep. Joe Wilson's outburst.
Presidents didn't even address Congress between 1800, when John Adams held the job, and 1913, says Fred Beuttler, deputy historian at the House of Representatives, who calls the Wilson incident "highly unusual, if not unique."
"Occasionally, members of the opposing party have been known to boo and jeer as expressions of dissent on a specific point," says Beuttler, citing instances during the Bill Clinton and George W. Bush administrations. But before Wednesday, he says, "expressions of individual opposition of members to a president's speech had not been recorded."
Some have compared Wilson's outburst to those that occur routinely in Britain's House of Commons, when the prime minister is answering questions. But one political analyst says this is vastly different, because the prime minister isn't the head of state.
"Our president is the head of government and also the head of state, the combination of the country and the government," says Steven Cohen, professor of public administration at Columbia University. "We expect a certain amount of deference to the president, in the same way as we would for the queen. Here, we combine the two roles."
To another political analyst, it's the nature of the accusation - an elected official calling the president a liar - that is not only a serious breach (accusations of lying are forbidden under House rules) but also extremely rare in politics.
"Accusing someone of lying is impugning their integrity," says Kathleen Hall Jamieson, an expert on political communication at the Annenberg Public Policy Center at the University of Pennsylvania. "It was done in print a lot in the 19th century. But it is not routinely done in political discourse."
Congress is a place of deliberation, Jamieson adds: "If you call someone a liar, you've ended the deliberations. This is such a strong norm that it's been in the House rules since Jefferson."
In Britain, too, despite its lively parliament sessions, lawmakers can be suspended for accusing others of lying. One, Tam Dalyell, was thrown out for doing just that to former Prime Minister Margaret Thatcher, whom he called "a bounder, a liar, a deceiver, a cheat and a crook."
A British lawmaker was rebuked in 1986 for referring to President Ronald Reagan as Thatcher's "cretinous friend."
Winston Churchill was more subtle about the charge of lying, once describing a statement by another lawmaker as a "terminological inexactitude," now a commonly accepted euphemism for a lie.
Churchill was much subtler than the Labour lawmaker who accused Thatcher of acting "with the sensitivity of a sex-starved boa-constrictor." Or the members threatened with suspension for using terms including "hooligan," "cad," "jackass," "Pecksniffian cant," "coward," "git," "guttersnipe," "stool pigeon" and "traitor." Or Prime Minister John Major, who called Tony Blair, then the opposition leader, a "dimwit."
And royalty hasn't been exempt: The late Willie Hamilton, a Labour MP, was ordered to retract his description of Prince Charles as "that young twerp."
In Asia, it can get physical - all-out brawls are almost an annual event in Taiwan's raucous legislature, where in May 2007, lawmakers exchanged punches, climbed on each other's shoulders and jostled violently during a debate over electoral reform.
In Seoul, hundreds of lawmakers screamed and wrestled in South Korea's parliament in July, scuffling and shouting, grabbing each other by the neck and trying to bring opponents to the floor. Last year, lawmakers used sledgehammers to pound their way into a parliamentary committee room.
In Hong Kong, meanwhile, maverick lawmaker Raymond Wong, nicknamed "Mad Dog," hurled a bunch of bananas across the legislative chamber to protest an old-age allowance scheme.
And in Israel, parliament speeches are often drowned out by shouting legislators leaping out of their seats, pointing fingers and running about the chamber or being ordered out by the speaker. In 2001, Ethics Committee chairwoman Colette Avital circulated a list of 68 insults she wanted banned, including: blood-drinker, boor, fascist, filth, eye-gouger, Jew-hater, Nazi, Philistine, terrorist, traitor and poodle.
Such colorful drama is less familiar to Americans these days, at least since an 1858 debate over allowing Kansas as a state.
"A brawl ensued on the House floor with 50 or more representatives rushing towards one another and wrestling and punching each other as the Speaker, James Orr of South Carolina, pleaded for order," says Beuttler, though he notes the fight ended in laughter as one congressman pulled the wig off another, "which set the whole House of Representatives roaring with laughter."
Recent years have been much less colorful - until this week, and Wilson's remark, the fallout from which continues to saturate the airwaves and the blogosphere.
Many have blamed a culture of talk radio, the Internet and cable TV, where everyone has a point of a view and a platform, for creating an environment where such an incident could happen.
"If we become accustomed to hearing people call a politician a liar everywhere else - for example, in town halls - suddenly it seems more natural in a place where it's never been acceptable," says Jamieson,
But with any luck, she and others say, Wilson's remark may actually serve to prevent future such outbursts, because the swift negative reaction was a powerful reminder of what is not OK.
"I'd imagine that the next time President Obama speaks to Congress," says Beuttler, "everybody will be very polite."
Associated Press writers Robert Barr, Meera Selva, Kwang-Tae Kim, Dikky Sin, Peter Enav and Ian Deitch contributed to this report.
Some 150 years ago, a congressman from South Carolina, angered by a speech on slavery, entered the Senate chamber and beat a senator from Massachusetts into unconsciousness with a metal-topped wooden cane.