Two doctors aboard space shuttle Columbia cut into the legs of six anaesthesised baby rats as part of a study of how nerves develop in weight-lessness.It was the first surgery ever performed in space on creatures meant to survive. Previously, astronauts merely dissected dead animals. The death count rose yesterday to 52, more than half of the 96 baby rats launched aboard Columbia two weeks ago. The cause of death: low blood sugar, low body temperature and dehydration, all due to maternal neglect.