Psychopathia Sexualis, written by Richard Freiherr von Krafft-Ebing in 1886, is a pioneering work in the field of sexual pathology. This clinical-forensic study delves into a wide range of paraphilias and specifically focuses on male homosexuality and bisexuality—referred to as the “antipathetic sexual instinct” in the subtitle.
Crossdressing in the modern sense appeared with Karl Heinrich Ulrich as early as 1868, and Carl Westphal used the term "contrary sexual feeling" in 1870, although not yet differentiated from so-called uranism. Richard von Krafft-Ebing then published the first edition of "Psychopathia sexualismus" in 1886, which went through 17 editions. There he uses the term “Metamorphosis sexualis paranoica” (sex change madness).