Charles Darwin did not know much about medicine (and neither did any of his contemporaries) but he took plenty of it. Soon after his return from the voyage on HMS Beagle he was struck down by a mysterious illness. Much energy has been expended on deciding what it might have been—a supposed conflict between Christian belief and rationalism, a parasite picked up in Brazil, or even, some say, the obsessive swallowing of air. The great man's lat ...