As a fountain of health eroticism in old age has a positive effect for women ( respectively men ) on 10 ( respectively 7 ) different areas of health. At the same time, as a fountain of youth, it leads to a considerable extension of life. The author gives the readers a tip on how to use this extended lifetime to benefit from a bubbling source of money for the rest of their lives through a certain contract. The framework of the book is the love story written in the form of an exchange of letters.