For uncircumcised males, stimulation of the penis in this way comes from the pumping of the foreskin, in which the foreskin is held and slid up and down over the glans, which depending on foreskin length, is completely or partially covered and then uncovered in a rapid motion. Although pornography has usually focused on heterosexuality, due to the prevalence of the heterosexual orientation, explicit gay material has a long history as well, which reaches back to Greek antiquity, if not to prehistory. Mammary intercourse is said by Alex Comfort to produce mutual orgasm in women with sensitive breasts , and it was one of the nine substitute exercises for penetrative sexual activities, as detailed in the Paradis Charnels of 1903. Clothed female, naked male is a genre of erotica featuring one or more nude men and one or more clothed women. It may involve sexual attraction to women who are pregnant or appear gay sex video pregnant, attraction hentai sex to lactation, or attraction to particular stages of pregnancy such as impregnation or childbirth. Some restrict a policy of panties/nipple tape for females and some allow full nudity with explicit sexual interaction allowed. Some do not use mature milfs the diapers at all, for arousal, or bladder and bowel movements. Another variant of reality pornography consists of normal couples that are filmed by professionals, in which case the only obvious distinction from amateur pornography is the higher quality of production, filming and editing. Homi Bhabha defined the idea of a racial fetish in contrast to the idea of the Freudian sexual fetish which he describes a denial of difference, where the male sees the female as a castrated male, seeing missing parts rather than a different anatomy. To tea bag is a slang term for the sexual act of a man placing his scrotum in the mouth of a willing sexual partner for pleasure or onto the face or head of another person. As with most forms of sexual activity, anal sex participants risk contracting sexually transmitted infections .