Assistance animals – from guide dogs to psychiatric service cats – unlike computerised machines, can establish a natural symbiosis with the patients who rely on them. Could animals be transformed into medical devices? This project proposes using animals bred commercially for consumption or entertainment as companions and providers of external organ replacement. The use of transgenic farm animals, or retired working dogs, as life support ‘devices’ for renal and respiratory patients offers an alternative to inhumane medical therapies. Could a transgenic animal function as a whole mechanism and not simply supply the parts? Could humans become parasites and live off another organism’s bodily functions?