Auguste-Henri Forel (September 1, 1848 – July 27, 1931) was a Swiss myrmecologist, neuroanatomist, psychiatrist and eugenicist, notable for his investigations into the structure of the human brain and that of ants. For example, he is considered a co-founder of the neuron theory. Forel is also known for his early contributions to sexology and psychology.From 1978 until 2000 Forel’s image appeared on the 1000 Swiss franc banknote.