Art BRYAN KNEALE Royal West of England Academy, Bristol

Bryan Kneale is a chameleon. A talented artistic all-rounder, who, this year, as he retires from the chair of drawing at the RCA, abandons his third incarnation in half a century. To mark the event, he is being honoured with an exhibition in Bristol.

Although, in his time, Kneale has been both draughtsman and sculptor, it was as a painter that he first achieved prominence in the 1950s with a series of memorable exhibitions at the Redfern Gallery. For a decade, he doggedly pursued the career of a portrait-painter. He was never a mere flatterer, rather he was always intent on uncovering the truth behind the stoical facades of his increasingly celebrated sitters. What is most evident in the portraits on view here, though, is a sense of frustration, and it is not entirely surprising that in 1960 Kneale should have changed his medium to that of sculpture.

It was not, as we might have supposed, portrait bronzes that engaged Kneale's immediate attention, but semi-abstract works in twisted iron and bronze. Certainly the human form was drawn upon, as in a particularly moving sculpture of a fellow hospital patient caught at the moment of death. Chief in Kneale's mind, though, was always a concern to understand the way in which even the simplest form can contain some organic element. In Balance, (1988), for example, although the artist is dealing ostensibly with an abstract concept, the shape with which he responds to that subject takes on a bird-like presence. The same can be said of a fine wall piece of the following year - which is both a classic exercise in formal containment and an evocation of birth, regeneration and movement.

In 1990, Kneale took up the post of First Professor of Drawing at the RCA. It was a controversial new appointment at a time when the cutting edge of contemporary British art seemed to be increasingly conditioned by a trend towards the conceptual, but Kneale rose to the challenge with ease.The choice proved to be inspired. Kneale has always been a draughtsman at heart. From the start his aim has been to uncover the structure of anything which confronts him - to get to the nuts and bolts of humanity. In particular, Kneale likes bones. His drawings of birds and animals are an extraordinary achievement. Without flesh, fur or feathers, these creatures are reduced to skeletons which appear to have stood up and reassembled themselves. Spoonbill (1987) is as spare and unforgiving an image as any 15th-century allegory by Durer or Altdorfer, and might well be intended to convey a similar sense of sobering humanism.

In effect, these works, arguably Kneale's greatest achievement, are not life drawings, but "life in death" drawings, beautifully made, with a genuine feeling for form and brittle beauty. Kneale strips away the flesh and blood, the hair, the eyes and, implicitly, the soul, and presents the framework of life.If his work has an abiding message it is to always look beneath the surface. He reminds us that the essence of any living thing is no more than a heap of old bones.

n Royal West of England Academy, Bristol, (0117 973 5129) to 23 Sept