Senile dementia has been around for as long as people have had the means of recording it. While the average hu-man life span remained short and old age was a comparative rarity, senility was considered a natural by-product ofaging--perhaps the result of sclerotic cerebral arteries. The young German neuropathologist Alois Alzheimer believed he was witnessing an entirely new variety of mental illness when, in 1901, he admitted to his clinic a fifty-one-year-oldwoman, Auguste D., who was suffering from bizare mood swings and severe memory loss and who, in Alzheimer'sinitial examination of her, gave problematic answers to his questions: