Steve Connor: The mercury pills behind Abe's rage

Retrospective diagnosis is a game scientists and doctors sometimes play with one another. The aim is to work out the true medical condition affecting a character or event in history. So, for instance, was the Black Death in the 14th century due to bubonic plague? Or did Tutankhamun suffer from the congenital disorder Klippel-Feil syndrome, which results in the fusion of the vertebrae in the neck?

Franklin D Roosevelt's paralytic illness was said to have been the result of poliomyelitis, but another posthumous diagnosis suggests it may have been Guillain-Barré syndrome. Botulism has been posited as the cause of the religious experiences of the English mystic Julian of Norwich, and the madness of King George III has been blamed on the metabolic disorder porphyria, or was it lead poisoning?

Poor old Abe Lincoln has also suffered his fair share of retrospective diagnosis. His long limbs and sunken chest are classic symptoms of Marfan syndrome, an inherited disorder of the connective tissue. He is also supposed to have suffered from mercury poisoning as a result of taking "Little Blue Pills" to treat what some believe was clinical depression. Unfortunately the pills contained very high levels of mercury, a fact now established by the Royal Society of Chemistry, which analysed some specimens found in a Victorian pill chest kept in a Devon museum. They were found to contain up to 120 times the acceptable daily intake of mercury.

Lincoln was known for his towering rages, something that may have been caused by high levels of mercury in his body. Fortunately he abandoned the medication before the outbreak of the American Civil War because the pills "made him cross". The rest, as they say, is history.

An authority on acronyms

Britain now has its own space agency, complete with zippy logo of a rocket-propelled red arrow launching majestically through the red, white and blue shards of the Union Jack. The UK Space Agency replaces the British National Space Centre – it was always a bit galling other European countries had space "agencies", while we had to make do with a mere "centre".

Yet America's space agency, Nasa, is actually an "administration", despite the fact it has often been mislabelled as the National Aeronautics and Space Agency.

It's easy to get these things wrong. Gordon Brown slipped up the other day when he said the Sellafield nuclear plant will be open to inspection by the International Atomic Energy Authority. In fact the IAEA is a UN agency – an important distinction if you care about these things. Brown's speechwriter was evidently distracted by the existence of the UKAEA, the UK Atomic Energy Authority.

Science is rarely simple

Scientists love to make things complicated when simplicity would do so much better. Take a recent study into compulsive eating and addiction among laboratory rats. The animals were given "an aversive conditioned stimulus that predicts negative outcome" to test their love of junk food. That's a small electric shock to the rest of us.