ART / The child in time: James Hall on the touring exhibition 'Innocence and Experience' and Rembrandt's Girl at a Window at Dulwich Picture Gallery

THIS summer, one of the most sensational and original of recent art historical studies - Leo Steinberg's The Sexuality of Christ in Renaissance Art and in Modern Oblivion - will be 10 years old. Though now remaindered, this iconoclastic tome hit the headlines at the time, and even got a respectful review from the then Director of the National Gallery, Michael Levey.

Like Vladimir Nabokov, Steinberg was a Russian emigre who studied in England before becoming a professor at an American university; again like Nabokov, Steinberg confronted an issue which had, he said, been 'long-suppressed'. His thesis was that Renaissance art produced 'a large body of devotional imagery in which the genitalia of the Christ Child, or of the dead Christ, receive such demonstrative emphasis that one must recognise an ostentatio genitalium comparable to the canonic ostentatio vulnerum, the showing forth of the wounds'. Steinberg claimed that in hundreds of religious works painted before the Reformation (Correggio's Madonna of the Basket and Botticelli's Adoration of the Magi, both in the National Gallery, are cited) the 'ostensive unveiling of the Child's sex, or the touching, protecting and presentation of it, is the main action'. The significance of the procedure was theological. It proved the Christ Child's humanity and manhood.

This thesis is a typical product of our post-Freudian age. Childhood is revisited, and if all goes according to plan, it is found to be stuffed full of 'adult' features and phenomena. As a result, adult and infantile worlds no longer seem so clearly demarcated. In some respects, they have got too close for comfort, and precociousness - that key attribute of children - is both admired and feared.

'Innocence and Experience', a major touring exhibition which is currently at the Castle Museum, Nottingham, comprises over 60 images of children in British art from 1600 to the present day. The exhibition has been divided thematically, and it amply demonstrates the wide variety of psycho-sexual hoops that children have been put through down the centuries. It is not always a pretty sight.

The first section, 'The Family', kicks off with a juxtaposition of contemporary and Victorian mother-and-child pictures - Helen Chadwick's One Flesh (1985) and William Mulready's The Lesson (1859). The former is a darkly sumptuous montage of colour photocopies taken from life. It is a feminist update of the standard Madonna & Child package, and features a dramatic and witty act of ostentatio. A half-length seated woman (a friend of the artist) has been decked out in flowing robes. Bleary-eyed with contentment, she breast-feeds her baby. Yet romantic reverie coexists with biology. Not only does a brown-coloured placenta hang over her head like an autumn leaf, but the child's umbilical cord still dangles from its navel. The mother is poised with a pair of scissors to snip it. Meanwhile, her free hand points towards the child's genitals. What we see is both miraculous and scandalous, for 'He' is most definitely a 'She'.

Nevertheless, Chadwick seems somewhat ambivalent about the coup. Her title, One Flesh, implies that the mother and daughter are an inseparable, autonomous family unit, and that inception and birth take place without outside interference. Yet the duo are not exactly a picture of health. They are mere photocopies with sepia skin; their existence is threatened with instant obsolescence.

Mulready's lozenge-shaped painting, The Lesson, is an earlier attempt to represent a modern kind of self-sufficiency. Inspired by some of the educational ideas of Godwin and Blake, the picture asserts the importance of matriarchal tuition in a healthy home environment. A boy sits bolt upright on a young woman's lap in an idyllic garden setting. He is naked, except for a white cloth that has conveniently fallen across his loins, thus saving the blushes of Victorian ladies. He gazes intently at his mother, a lovely lady who must surely be on loan from a Raphael altar-piece. She is teaching him how to pray.

Sadly, the child is trapped in a physical and emotional limbo. This is because Mulready needs him to be old enough to be a passable imitation of a sycophantic swot, and young enough to be a passable imitation of a Christ Child. The net result is an anatomical oddity. The Ingres- esque elongations of his back and left leg don't quite tally with the pneumatic puppy-fat on his belly and thighs. No wonder his mother prods his spine and wrist so gingerly.

The next section - 'A Sense of Identity' - focuses on portraits of children. Of these, the best known is Van Dyck's Five Children of Charles II (1636-7). It is represented here by a contemporary studio copy. The children, shown in three- quarter length, are distributed across a long, rectangular canvas. Despite its easy sensuality, the picture is choreographed according to a ruthless law known as The Divine Right of Kids.

A remarkably low viewpoint serves to elevate all the children way beyond their years. At the same time, they are classified according to their age and sex. The older they are, the more solemn they get. Extreme youth equals naughty nature. On the right a baby girl, limbs akimbo, is being played with by the second youngest sister. The baby reaches out to a huge dog. Behind them is an unkempt bowl of leaves, and beyond, bushy trees.

Elsewhere, the cast and the decor behave themselves. On the left and in the centre, the three eldest children stand to attention in front of a thick curtain. The future Charles II is the eyes-front stiff in the centre. The dainty fingers on his left hand are laid on the dog's forehead, and, as though by magic, the brute is utterly submissive. We get the picture - today the mastiff, tomorrow the masses . . .

The last section - 'The End of Innocence' - is much the most disturbing. It focuses on works that deal with the end of childhood in the physical and psychological sense. In the case of Millais's sultry Autumn Leaves (1855-6), Lely's slick portrait of the eight-year-old Lady Charlotte Fitzroy (c 1672), and Gilbert & George's acidic Berryboy (1984), children are juxtaposed with ripe fruit. They are there for the taking or leaving. All three might be defended on the grounds that they are forms of social realism - they document the way things are, the way societies and biologies work. Alternatively, you might argue that these works, made by adults for adults, glamorise and perpetuate a thoroughly exploitative system.

That is the conclusion you are asked to come to with Peter Blake's Daimler. This utterly creepy picture was commissioned by Jaguar Daimler in 1980, and reproductions of it were given to every customer. Sylph-like prepubescent and adolescent girls clad in see-through lingerie are dispersed in a field lit by a full moon. Some stare at a dark Daimler that is parked in the top corner of the picture, while others look wistfully and even complicitly out at the viewer. Yet Blake doesn't leave it at that. He has painted a personalised number plate on the car, 'PB1'. When it comes to the formation and fulfilment of fantasies, Peter Blake puts himself - the artist - in the driving-seat.

There is another, more mundane way in which artists might be said to contribute to the maltreatment and misrepresentation of children. They just won't sit still. Most artists force them to, and, accordingly, the artifice of sitting for a portrait comes through into the portrait.

This could explain why so few portraits of living children carry any conviction. Dead children are another matter. Indeed, the most moving picture in this exhibition is Allan Ramsay's Sketch of a Dead Child (c 1743). All he has painted is the sleepy, Buddha-like head of his dead son. The condensed memory of him is a soft oasis in a desert of bare canvas.

From tomorrow, a ramshackle but enjoyable exhibition at the Dulwich Picture Gallery explores the meaning and legacy of Rembrandt's Girl at a Window. It is one of the most mysterious and copied pictures in the collection. A young girl wearing a loose white blouse leans on a ledge. The ledge is diagonal to the picture plane, but her head is turned towards us. With her left hand, she plays with her necklace. It is not even clear whether she is at a window, for the ledge is not anchored to any window frame or wall. Opinion is divided as to whether she is meant to be pensive or flirtatious, a day-dreamer or a prostitute.

Its impact was first felt in 18th-century France when it was in a Parisian collection. In La Jardiniere (1709) Jean- Baptiste Santerre tried to tidy the girl up by placing a basket of onions on the ledge and thus showing her to be a kitchen maid. But when the engraver Louis de Surugue copied Santerre's copy 10 years later, he replaced the onions with a creeper, turned the anonymous maid into Sylvie, a character from the Commedia dell'arte, and captioned the image with a love poem.

After Rembrandt's picture arrived in England in the 1770s, it exerted a considerable influence on English and American artists (unfortunately the gallery has not been able to get the copy by Reynolds and those of the sentimentalising American Rembrandt Peale). The finest tribute to its enigmatic allure is a description by a British critic from 1822: 'In the very lowest classes of life, and at an early age, before the sexual qualities become developed, you frequently see faces that exhibit no mark of sex whatsoever; and others (as in the instance before us) in which females, from associating indiscriminately with males, and partaking in the same sports and pursuits, acquire the same expression of countenance. The picture might just as well have been called Boy at a Window as Girl.' As usual, it's back to the drawing-board.

(Photographs omitted)