Not all dust will return to dust when the pickled corpse of Vladimir Ilich Lenin leaves its glass sarcophagus in Red Square to rot in the soil of St Petersburg cemetery next to the bones of his mother.

Lenin's brain, the source of the Bolshevik revolution, will endure - sliced like prosciutto into 31,000 slithers, mounted on glass and stored behind three locked doors, each reinforced with metal and fitted with an alarm, in Room 19 of the Moscow Brain Institute.

Wafers of Stalin's brain are kept down the hall. Bits belonging to Vladimir Mayakovsky, the revolutionary poet who shot himself, are preserved next door. And the brain of the physicist and dissident Andrei Sakharov - proof that the institute is not impervious to time - is being cut into microscope-size chunks in another room.

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The prize, though, is Lenin. 'No brain has ever been studied so closely,' gushes the director, 70-year-old Oleg Adrianov. An institute veteran of 32 years, he keeps a wood-cut print of Lenin - alive and pensive - on the wall above his desk. He explains: 'I am much obliged to Lenin's brain. But it has nothing to do with politics.' He says he would much rather have studied Mozart. Freed from the taboos that bound his three predecessors, Dr Adrianov has just published the first account of Lenin brain studies in Successes in Physiological Sciences, the journal of the Russian Academy of Medical Sciences. Its main conclusion: Lenin's brain was nothing special.

He had a big frontal lobe and a 'large number of especially big pyramidal neurons' but, says Dr Adrianov, 'all we can do is speculate about what this means'. He is still more dismissive about Stalin: 'It offers nothing.' Far more intriguing, he says, are the brains of deaf mutes.

This is not what the Communist Party had in mind when in 1926 it invited Oskar Vogt, a pioneering German neurologist, to help unlock the keys to Lenin's genius. The Brain Institute's main handicap today is poverty, not ideological mumbo-jumbo. A special microscope with a video display imported from Austria is broken. Its brain slicer, custom built but which could do service in a New York deli, is wonky. Laboratory staff in white coats eat their lunch next to jam jars floating with whole and fragmented brains.

But whatever is happening to his body and his political reputation, Lenin's brain is treated with more respect. It is kept on the third floor in two large roll-top wooden cabinets. Each has dozens of meticulously labelled drawers. ('Right hemisphere, 1-18 block, sections 1-35,' reads a handwritten card on one.) Around 1,000 have been stained purple and black for study under microscopes. The vast majority, though, are a milky grey, unsullied and awaiting new techniques to probe the mysteries of Lenin's thought.

Next to a window, shielded by a padlocked metal shutter, stands another cabinet. It holds 14 large volumes bound in thick green leather and embossed in the top right hand corner with a single word: LENIN. They contain what used to be one of the most sensitive of Soviet secrets - a detailed map of Lenin's brain. If Marxism was a science, reason was its tool. And Lenin's brain was its ultimate weapon.

The brain itself is shrivelled and small. No cross-section is bigger than a baby's fist. Large sections of the left hemisphere were damaged by a series of strokes and these patches have been coloured with dark ink in photographs. But Dr Adrianov dismisses as 'muckraking rubbish' rumours that it was eaten away by syphilis. 'A brain is like a water-melon,' he says, '95 per cent of it is liquid.' But he adds: 'Frankly, I do not think he was a genius.' He offers a once classified detail: Lenin's brain weighed 1,340 grams. This makes it lighter than Turgenev's two-kilo monster but heavier than Anatole France's puny 970 grams. A dusty museum downstairs devotes much attention to this problem, displaying a 7kg elephant brain in a vat of murky green fluid along with a jars of unborn foetuses to illustrate brain development.

Lenin died on 21 January 1924. He had been ill since the summer of 1922, when he suffered the first of at least five strokes. His last recorded words, uttered during a sleigh ride outside his country house near Moscow, did not suggest immortal genius: 'Good Dog.' The autopsy, conducted the same day, took over four hours. Cause of death: brain haemorrhage.

After two months of squabbling, it was announced in March 1924 that the Communist Party had 'decided to take all measures available in current science to preserve the body for as long as possible'. The state Funeral Commission promptly became the Commission for the Immortalisation of the Memory of VI Ulyanov (Lenin). The decision was inspired in part by the pharaoh Tutankhamun, whose mummified remains had recently been found by Lord Carnarvon near Luxor on the Nile. In August, the first Lenin Mausoleum opened in Red Square.

The party became obsessed with Lenin's immortality. 'Lenin lived, Lenin lives, and Lenin will live,' ran a favourite slogan. Maxim Gorky celebrated the mysterious after-life working of Lenin's brain: 'Vladimir Lenin died: the heritage of his reason will live on, are alive, and work successfully as no one, nowhere, in the world ever worked.'

The brain itself spent two years in formaldehyde. No one dared to discard it. But no one knew what to do with it. Vogt, the German professor, offered a solution. He helped to set up a small laboratory in 1926, and two years later was given a spacious brick building confiscated from an American business to establish the Brain Institute.

Lenin's brain was chopped into four parts and each of these sliced into 7,500 sections. Vogt returned to Germany in the Thirties and research continued under two star pupils, Ivan Filimonov and Semen Sassikov. Scores of other brains were brought in for study and comparison with Lenin's.

The original theory behind Vogt's work - a belief in direct links between brain structure and intelligence - has since been discredited. 'You cannot tell from a dead brain whether it belong to a man or woman, or even a chimpanzee or human,' says Stephen Rose, director of the brain and behaviour research group at the Open University. But he pays tribute to other work done at the Institute by the Moscow scientists. And unlike phrenology, the notorious pseudo-science based on skull measurements, brain research in Moscow did not, despite strong pressure, ally itself openly with racial or political purges.

Apart from a brief research note published by Vogt in 1929 in a German scientific journal, none of the work done on Lenin's brain made it into print until Dr Adrianov's essay, based largely on a secret 1967 paper. There were repeated pleas for more openness - letters to the Communist Party in 1967 and 1969 and to then the Academy of Medical Sciences after 1980. All were rebuffed. 'I do not understand why my teachers could not publish,' says Dr Adrianov. 'There are so many secrets in this country that make no sense.'

The biggest secret is that Lenin's brain was, in the end, just a brain. More than six decades of research at the Brain Institute have led to one firm conclusion: the dazzling indivividuality of every brain. 'Cognitive activity, even less behaviour, does not directly relate to brain morphology,' says the director. 'This was a rude simplification.'

All the same, he objects to the suggestion that Lenin's brain should perhaps follow what, in the next few months, is likely to be the fate of his body. The brain slices should be preserved. 'They are in excellent condition. They can be kept for ever.' Particularly valuable, he says, are the slices not stained with dye. 'There is still much work to do. They can be examined in the future when science discovers new methods. I don't think anyone wants to take them away from us.'

So Lenin, in this respect at least lives. Does Dr Adrianov have any interest in studying the brains of, say, Gorbachev or Yeltsin? 'None whatsoever. We have done enough politicians. They are not the most interesting brains.'

(Photograph omitted)