The exact source and nature of the fluid continue to be a topic of debate among medical professionals, which is also related to doubts over the existence of the G-Spot. Practitioners have described going to public places such as a mall or a park. The Japanese sex industry uses the term Paizuri . This category also includes pornographic home movies. It is also often mixed with other fetishes in practice, such as voyeurism, denial, etc. One or more of the participants may engage in autoerotic sexual activity, such as masturbation, possibly without physical contact with the other participants. Anal sex or anal intercourse is generally the insertion and thrusting of the erect penis into a person anus, or anus and rectum, for sexual pleasure. POV pornography involves camera angles designed to provide the viewer a view similar to that seen by one of the participants, whose face is never shown. The speed of the hand motion will vary from person to person, although it is not uncommon for the speed to increase as ejaculation nears and for it to decrease during the ejaculation itself. Insertion in pornography features gay fuck women inserting various odd objects into their anus or nude milfs vaginas. After the prerequisite level of sexual stimulation has been achieved, and ejaculation becomes imminent, the male will position his penis so that the semen discharged will be deposited onto his partner face. The legal status of masturbation has also varied through history and masturbation in public is illegal in most countries. Kinbaku is a Japanese style of bondage or BDSM which involves tying up the bottom using simple yet visually intricate patterns, usually with several pieces of thin rope . In the 1920s, Havelock Ellis reported that turn-of-the-century seamstresses using treadle-operated sewing machines could achieve orgasm by sitting near the edge of their chairs. The first pegging scene appears to have been in the non-pornographic 1970 film Myra Breckinridge, based on the novel hentai sex of the same name by Gore Vidal, although it was not explicit.