She focused on the beauty of women and proclaimed her love for girls. The terms lesbian, invert and homosexual were interchangeable with sapphist and sapphism around the turn of the 20th century. In the middle of the 19th century, medical writers attempted to establish ways to identify male homosexuality, which was considered a significant social problem in most Western societies. In categorizing behavior that indicated what was referred to as " inversion " by German sexologist Magnus Hirschfeld , researchers categorized what was normal sexual behavior for men and women, and therefore to what extent men and women varied from the "perfect male sexual type" and the "perfect female sexual type". In some cases, it was not acknowledged to exist. However, sexologists Richard von Krafft-Ebing from Germany, and Britain's Havelock Ellis wrote some of the earliest and more enduring categorizations of female same-sex attraction , approaching it as a form of insanity Ellis' categorization of "lesbianism" as a medical problem is now discredited.