Psychiatrist Avicenna had a malnourished patient who believed he was a cow ready to be slaughtered. Avicenna, impersonating a butcher, came to kill him but said the cow was too lean and had to eat more. The patient ate more food which restored his health and cured the delusion.
A girl obsessed with biting her nails was convince by a hypnotist to let them grow to get more enjoyment from biting them. After letting them grow, she no longer wanted to bite them, thus curing her obsession.