Richard Freiherr von Krafft-Ebing
Originally published in 1886, Psychopathia Sexualis was translated from the original German and continually updated until 1965. The following extract has been reprinted from the 1906 edition.
Psychopathia Sexualis concerns itself with all manner of sexual abberations, including a number of case studies categorized under various sub-headings. Under "Sexual Inclination Toward the Opposite Sex," we find an entry for Jack the Ripper listed as Case #17. It includes a brief summation of the murders and suggests that, for the Ripper, "the murderous act and subsequent mutilation of the corpse were equivalents for the sexual act."
Case 17. Jack the Ripper. - On December 1, 1887, July 7, August 8, September 30, one day in the month of October and on the 9th of November, 1888; on the 1st of June, the 17th of July and the 10th of September, 1889, the bodies of women were found in various lonely quarters of London ripped open and mutilated in a peculiar fashion. The murderer has never been found. It is probable that he first cut the throats of his victims, then ripped open the abdomen and groped among the intestines. In some instances he cut off the genitals and carried them away; in others he only tore them to pieces and left them behind. He does not seem to have had sexual intercourse with his victims, but very likely the murderous act and subsequent mutilation of the corpse were equivalents for the sexual act. (McDonald, le criminal type, 2 edit., Lyon, 1884; Spitzka, The Journal of Mental and Nervous Diseases, 1888, December; - Kierman, The Medical Standard, 1888, Nov. and Dec.)