Now you may put this down to a young artist's oversight, but I'm not sure. Ingres (for it is he) was a precocious painter. The oversights of his youth aren't overcome. They turn into the idiosyncrasies of his maturity. He was one of the smartest and most intense of European portrait painters. He could summon up the human presence as few others could. He also had very strong and funny feelings about the human form.
This wasn't always obvious. Jean- Auguste-Dominique Ingres (1780-1867) used to be one of painting's straight men, the epitome of the slick, the smooth, the square, the 19th-century academic artist par excellence. What that view saw was his formality, his high micro-finish, his astonishingly sensitive rendering of tone and texture - and his unflinching flattery of the pride and property of his bourgeois sitters. Rightly: without those qualities, technical and moral, the portraits would be nothing.
But going round Portraits by Ingres, which opens at the National Gallery tomorrow, dwelling on one astonishing creation after another, you're conscious at the same time of other agendas which can hardly be called hidden.
The show's opening knock-out blow is Napoleon on his Imperial Throne, done when the artist was 26. Flattery on the grandest scale, you might say, a triumph of golden regalia and tassels, red velvet, white fur and satin. But then, think: Bokassa, or some other self-made-up emperor. That's what Napoleon was. And Ingres' picture, with its highly artificial display of the attributes of kingship, on the verge of collapsing into an assemblage of rich bits, might almost be mockery, a royalist satire on this Corsican oik, decking himself out in the robes of Charlemagne: a fabricated image of a fabricated authority.
So much for power. As for sex - I don't know that there's a name for Ingres' sexual imagination. It's embodied, almost fully formed, in the 17-year-old's portrait drawing of Barbara Bansi. What's she like? Her upper half is a Frankenstein's monster of idealisations, beauty formulas combined into deformity. The head which seems to be only a swelling on top of the neck, the smoothly arcing shoulder that starts to resemble a humped back, the breasts so high that they project from the collarbone - such is Ingres' model woman, the doll he realises again and again in his mythological fantasies, and which always inflects his pictures of real women, too.
Their voluptuousness isn't only a matter of shape. They are lapped in luxury, a sensuous opulence into which their bodies half-disintegrate. The oval image of Madame Riviere is like a sweet-jar, full of bon-bons and jujubes - a pile-up of gorgeous stuffs, and among them some pieces of fine, plump flesh. A moral critique here is both obvious and powerless. It is evident that this is bourgeois portraiture supreme: a perfect marriage of sex and money, a melange of expensive fabric and expensive skin, the wife a pampered chattel among chattels. But whatever you say, the pictures only reply: "indeed - and how beautiful, how delicious".
But there are more curious goings-on, which begin to exceed anything Ingres' patrons might have demanded. Look at the dreamy features of Madame de Senonnes; how they seem to be not quite fixed to her head, to swim, to float in the pool of her face. Or look at her velvet-sleeved right arm, enormously long, apparently lifeless, just laid in her lap. Something very strange happens to these ladies' limbs. They go soft and limp. They seem to be filleted, or like empty skins filled with water, lolling. They often don't seem to be properly attached to the rest of the bodies.
These tender morsels of swelling chubbiness are part of a general air of molestation and innuendo, of voyeurism - or its tactile equivalent - as in accidentally on purpose rubbing or pressing up against someone's body in a crowd. The dresses and pillows are primped and patted and flounced and tweaked and plumped. (Ingres is the great peintre-couturier. He loved a frock, and got actively involved in what his sitters wore.) His compositions themselves are full of pictorial tucks and nudges: little clusters of sharply rendered accessories that poke in at the corner, or peep out behind someone's back. And this feeling is then picked up by the brushwork, too. The exquisite, meticulous finish of each depicted surface becomes, as it were, the painter's finishing touch.
It's all very close to that passage of soft-porn parody in Ulysses, where "several highly respectable Dublin ladies" complain of Leopold Bloom's unwanted attentions. "He said that he had seen from the gods my peerless globes as I sat in a box of the Theatre Royal... He lauded almost extravagantly my nether extremities, my swelling calves in silk hose drawn up to the limit, and eulogised glowingly my other hidden treasures in priceless lace..." In Ingres, too, it's the stately poshness of the women that pricks on the fantasy. In Ingres, too, there's the consciousness that a clothed body is a naked body touched all over. These are portraits in which at every point - to use the old divorce-court phrase - intimacy occurs.
Is it only women who get such treatment from Ingres? I would have thought so. But a fellow critic said that she got this feeling off the male portraits too, and I can see it in some of them. The spreading, placid features of Joseph-Antoine Moltedo seem to lack a supporting skull. His soft-brushed brown coat seems to lack a body inside it. But for a masterfully ambiguous study in masculinity, the portrait Louis-Francois Bertin has no rival.
Look at the way clothing and furniture feel their way round his stout and imposing figure. The sharp, curving edge of his high collar nicks his jowly chops. The smoothly curving edge of his chairback encases his circumference like the rim of a tub. Notice the patch of bright red chair- seat that peeps out just beneath his crotch, and sets off the dark contour of his trousered testicles - and then implies his whole, massive underside. Notice the oddly uncommanding nature of the hands-on-knees pose, the limp arms and stiff, crabby hands that seem to have been just gently placed in that position.
In the end, you have to say that Ingres had a thing (call it a vision, call it an obsession). It was a thing about power and passivity and impassivity, how they're all mixed up. In a way it's a natural concern for a bespoke portraitist - artist, sitter: who commands? who obeys? - but it goes deeper than that. It can take the form of worshipping sensual stupor, as in the extraordinary Washington portrait of Madame Moitessier, where she stands statuesque, her head and neck jawlessly fused, her face that of a dumb Roman matron's bust, her blank, lazy eyes drifting in divergent directions, her left arm hanging soft and dislocated, her shoulders quite asymmetrical under her dead-centre-parted hair-do, her underlip giving a sulky little pout. And I'm not sure what it's about, but it's absolutely enthralling.
`Portraits by Ingres - Images of an Epoch' is at the National Gallery, Trafalgar Square, London WC2, every day, tomorrow to 25 April; admission pounds 6, concessions pounds 4Reuse content