The essential thrust of heterosexuality in the male is return to the womb. Since the vagina is the only pathway to the uterus, the vagina becomes the center of sexual attention. Sexual concern with other anatomical structures (such as breasts for the rectum) is quite beside the point, and a substantial segment of the heterosexual subculture looks askance at nonvaginal sex. The heterosexual male thrusts fingers, tongue, and penis into the vagina in a desperate, irrational attempt to find again the security of the womb, to return physically to the womb. Since that attempt can never succeed, heterosexuality is inevitably unsatisfying. But to the extent that the male can re-enter the vagina, through which he traveled when he was expelled by his mother at his birth, heterosexual sex approaches satisfaction. This explains why coitus is the preferred form of heterosexual sex: the tongue cannot penetrate very far into the vagina (and besides, the vagina is a very unsatisfactory object of oralism, for the essence of oralism is taking things into the mouth, not straining the tongue to reach out). Nor can a finger penetrate far. Of the parts of the male body, and the thrust into the vagina, the penis reaches farthest toward the ultimate object, the womb. This fact, combined with the fact that many heterosexual males find pleasurable the sensation arising from the penis's contact with the walls of the vagina, works to push coitus as the prime form of heterosexual sex.