A dozen stout arms were toiling at the wall. It fell bodily. The corpse, already greatly decayed and clotted with gore, stood erect before the eyes of the spectators . . .

"The Black Cat," Edgar Allan Poe

For heavens's sake, why do people rob graves?

A few weeks ago someone stole Groucho Marx's urn from a sealed crypt in Los Angeles and left it the same night in another cemetery. Police assumed it was a prank. It was the second time thieves had made off with Groucho.

That's nothing. In 1978 two Eastern European political refugees dug up Charlie Chaplin in Switzerland and held him for ransom. Police caught them by staking out all the 200 public phone booths in Lausanne. During negotiations Charlie's price dropped from $600,000 to $250,000. The ghouls went to prison.

Is there something about dead comedians? But then, producer Mike Todd's unattractive remains, burned beyond recognition in a plane crash and sealed in a rubber bag, were dug up from his family plot outside Chicago in 1977. Police ruled out extortion and vandalism, concluding it was the work of "a very sick mind."

Edith Sitwell writes in "English Eccentrics" with appalling detail of how John Milton's grave was opened in 1790 by fans who removed hair, teeth, ribs and other souvenirs. Cowper and Leigh Hunt wrote poems addressing the mystique of the mementoes, taking the Romantic movement about as far as it could go.

You don't even have to be famous. A couple of Fairfax County teen- agers were caught digging in a rural family plot near Reston a few years ago, scattering bones around in a search for jewelry. They told the officers it was something they'd never done (and therefore had to do). The charge was sepulture, a felony.

Didn't we all know someone like that in high school?

Forensic experts agree from their experiences that most grave-robbing is done by vandals or youngsters who start with the exciting notion of drinking beer in the cemetery and then take off from there. In one case often cited by pathologists, Dr. Donald Jason, deputy medical examiner of Suffolk County, N.Y., was able to trace and return the skull of a 5-year-old girl that had been stolen from a mausoleum and left in the street.

Jason went to Dr. Lawrence Angel, the famous bone man of the Smithsonian, who detected coffin marks on the skull's forehead (from when the coffin collapsed on it) and eventually led to identification of the girl, who had died half a century before.

Jason recalled another case where a stolen skull was put on someone's bed. And there was the skeleton found in a Long Island basement, apparently left over from a fraternity initiation ceremony. Often such bones come from doctors' offices or medical schools.

"Highway crews turn up skeletons now and then," he said, "mostly Indians or old settlers. And of course there are the times a whole cemetery has to be moved."

Dr. Bertram Brown, senior psychiatrist for the Rand Corp. and former director of the National Institute of Mental Health, said that while "it's too grave a matter to say anything very lively," the motive of most crypt violators is "a need to go beyond limits, to be outrageous." He speculated that it stems from a drive to prove that there are no boundaries for the self, no challenge too great, no dare unacceptable, no taboo too sacrosanct. And surely the taboo against desecrating the dead is as old as the urn and barrow graves of the very earliest human communities.

Aside from vandals and pranksters, most grave robbers are in it for the money. These are the easiest to understand and therefore the least interesting. Still, the modern archeological thief does have a certain swagger. One anonymous expert in Etruscan graves recently told investigators about the special problems he has with the black market.

"Eighty percent of the items found in Etruscan tombs are obscene," he said, "so the non-obscene items have much more value. But the idiot tourist thinks because they are obscene they are more valuable. Therefore, the people who make fake Etruscan art specialize in obscene items, so instead of 80 percent of all Etruscan art being obscene, 120 percent is."

Archeological grave-robbing has become in recent years an international scandal, being perpetrated sometimes with the connivance of collectors and even some museums. But then, robbing graves for trinkets goes back to the pharaohs, as we know. The volume, let alone modern value, of treasures taken from Egyptian tombs is beyond comprehension. Remember the great international show, the golden cache of Tutankhamen, with its gorgeous death mask and cases full of priceless objects? That whole traveling exhibit was hardly a finger to what was left behind in the Cairo Museum: three life-size nested gold-walled rooms, golden chariots and thrones and sepulchres and necklaces and crowns: an emperor's ransom paid to Death.

And think about this: Tut died at 19 after a short reign as boy pharaoh and had to use a second-hand vault, designed for his vizier. Tut's tomb treasure--traditionally built up by legions of royal craftsmen from the day a pharaoh came to the throne--filled four chambers in a grave about 20 yards long.

Next time you're in Luxor stroll through the tomb of Sesostris I. He ruled for 14 years, and there was plenty of time to dig. His underground hall is as long as a football field, wide as a railroad car and has 14 chambers. It was empty when discovered, like all the others before Tut. Now stare down that marvelous, brilliantly painted passageway with its zodiacs and crocodile gods and starred ceilings, and try to imagine how it looked before the robbers got to it:

Was that entire space packed solid with gold and ivory?

Of course, for the hard-core grave robber, gold is just a sideline. Some pharaoh-thieves sought the mummies themselves for their alleged medicinal properties.

Many centuries later, a new market developed for bodies: Medical students needed them. (I mean, think about it: Would you want your brain operated on by a surgeon who had just read about it in a book?) In 19th-century Britain, for instance, professional ghouls supplied cadavers for medical schools. Dickens and Stevenson and others wrote of the Resurrection Men, a Victorian type as traditional as the Mudlarks who scavenged the Thames at low tide.

In that rather morbid climate, any person with an unusual physique became a magnet the minute he died. Charles Byrne, the Irish Giant, had arranged, before he died in 1783, to be buried at sea, but a noted London surgeon bribed the funeral guards and made off with the body for study. Eventually the skeleton was donated to the Royal College of Surgeons in London.

Inevitably, someone figured a way to cut out the middleman. In Edinburgh, the enterprising team of Burke and Hare sold cadavers to order. They were always very fresh, having been turned into cadavers by Burke and Hare themselves. It saved a lot of tedious digging.

But we are dealing here with mere tradespeople. The aristocrat of grave-robbers is the ghoul who does it for love. Since true necrophilia is so rare that there is virtually no literature on the subject and "no reliable reports on treatment," according to the encyclopedia, most of us hear about it only in stories. Authorities theorize it is related to a fear of sex and its possible consequences. Necrophiliacs, by the way, are invariably male.

Dr. Frankenstein doesn't count because he did it for science and doesn't seem to have enjoyed the work particularly. Edgar Allan Poe didn't exactly write about grave-robbing, but he appears to have had the authentic slavering necrophiliac spirit, with his repeated theme of beautiful women coming back from the dead, or appearing to, or being buried alive. Perhaps he never got over the death of his young wife.

"Hamlet," that charnel house, as Shakespearean scholar Harry Levin used to call it, reeks with images of feasting worms and rot, topped off with an actual grave-digging and the exhumation of poor Yorick. In "Romeo and Juliet" we visit a crypt filled not only with the skeletons of ancestors but with Tybalt in his bloody sheet and fresh-slain Paris. Shakespeare seems uncomfortable in "that nest of death, contagion and unnatural sleep" and never comes close to Wagner's overripe fascination with the love-death as a dramatic climax.

In any case, one can understand why grave-robbing is not as popular a crime as, say, car theft. There's not that much of a market for used people.