The idea of replacing body parts has attracted interest for a long time. In the third century, legend holds that St Cosmas and St Damian succeeded in grafting a leg from a recently deceased Ethiopian to replace onto the body of a patient. Unfortunately, this has not proved to be repeatable – the fact that the laboratory assistants in many representations of this event have wings indicating that a celestial connection may be required to make the operation more likely to succeed.

The more recent idea that it may be possible to take skin from a living person and, using the technique of cloning or nuclear transfer, make a replacement brain or heart is the focus of this Oration. Fig 1 illustrates the concept: the nucleus of a skin cell from the patient is transferred to an enucleated egg which forms an embryo. Embryonic stem cells (ESCs) can be derived from such an embryo and then directed into any tissue or organ desired. This theoretical scheme would give people new cells of their own genetic constitution, thereby avoiding problems of immunological rejection. This is an indication of the direction in which current research is moving at an encouraging pace.