As one who has difficulty peeing in a public loo, I look with awe on so brazen an act and it was hardly suprising that I should have immediately connected it with the photograph I saw later of Degas buttoning up his flies as he stepped out of a vespasienne. Had I discovered the scatology of Impressionism and Post-Impressionism? Was this the beginnings of a new study - away with Monet's gardens and menus, on with Renoir's Bidet, Cezanne's High Colonic, Pissarro's Pissoir.
Sadly, no further defecatory images have emerged and the idea has lain, becalmed in the malodourous sargasso of imbecilic book ideas - that is until the current exhibition of "Naked Shit Pictures" by the ever-outrageous Gilbert and George at Peckham's South London Gallery. From the close-ups of their exposed fundaments in the aptly entitled Bum Holes, to the erect penis formed from eliminated bodily waste, the two artists have given new life to a notion I had thought I had flushed away.
Of course there is nothing original about using the turd as a subject for art. In his history of Barcelona, Robert Hughes lets drop that his beloved Catalans have a folk character called the caganer or "shitter", a model of whom is often placed on Christmas creches where he is depicted as a peasant in a red cap, his trousers down, depositing a whorl of excrement on the expectant earth - for this figure is, as Hughes puts it, the "immemorial fecundator", nourishing the soil with his human manure. The Catalans honour the caganer's part in the cycle of sowing and harvesting and his presence can be traced in the early farm paintings of Mir and find echoes in some of the more outrageous works of his fellow Catalan Salvador Dali, whose faecal stains so shocked his colleagues that they held a solemn meeting to determine whether something so nasty had a place in surrealism.
But despite these precedents, it is impossible to forge a school - the Turdists say - out of such rare sightings. Even Picasso, who seldom missed an opportunity to startle, limited himself to a solitary portrait of his last wife, Jaqueline, having an ecstatic pee.
Far from looking to the past, G and G's latest work is another manifestation of that preoccupation with the body and its functions which seems to be settling in as the principle fin-de-siecle subject of our visual artists. From Helen Chadwick's Piss Flowers, the casts taken from the holes formed when she and her partner urinated into snow, to the video at the Tate by Mona Hatoum in which a medical view-finder takes us on a tour of her insides, we are being offered art which, its practitioners claim, is appropriate to the age of Aids, a time when the body and its well-being is a fetish of the chattering classes.
There is of course the shock element, the desire by our young artists to emulate the publicity-gathering success achieved by Duchamp when he exhibited a urinal as a work of art. The trouble is that we, the public, are getting to enjoy being teased - a dead sheep in formaldehyde passes from avant-garde act to the language of advertising in a nanosecond.
But is it the ultimate outrage? Almost certainly not, for when we grow used to one filthy surprise, an older, forgotten terror comes back to unnerve us. Today, death is probably the nastiest neurosis lurking in the background yet today's preoccupation with the crannies and fluids of the human body must finally lead to that cold slab in the dissecting chamber. This year's Edinburgh Festival saw the start of it with Andres Serrano's vivid photographs of cadavers - the podgy, pasty legs of a dead baby still bearing the imprint of too-tight ankle socks, the eye-sunken decomposing head of a corpse in a public morgue, and next month sees the opening of an international exhibition on "The Dead". Serrano began with Piss Christ, a crucifix in a bottle of his urine, which stirred up a firestorm of outrage, and has moved rapidly to death and decay. Why stay with human waste when you can have an entire digestive system rotting before your eyes?
n Gilbert and George's 'Naked Shit Pictures', to 15 Oct, South London Gallery (0171-703 6120); 'The Dead', to 7 Jan 1996, National Museum of Photography, Film and Television, Bradford (01274 727488); Andres Serrano's 'The Morgue and Other Works' to 23 Sept, Portfolio Gallery, Edinburgh (0131-220 1911) and on tour