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∙EXCITEMENT. The first physiologic response is erection of the nipples, from contraction of their muscular fibers. It occurs in both breasts, though not necessarily at the same time. Second, the pattern of veins in the surface of the breasts stands out more clearly, and this may extend to the adjoining chest wall. The breasts gradually increase in size as a result of the filling-up of blood vessels. In addition, the labia minora (the vulva's inner folds) turn bright pink, a process that Dr. Masters compares biologically with changes in female monkeys' exposed "sex skin." A lubricant appears in the vagina. As excitement proceeds to the next phase, the pigmented rings around the nipples (areolae) become engorged and impinge upon the erect nipples. The breasts increase in size by 20% to 25%. ∙PLATEAU. A pink mottling appears over the chest, spreads to the breasts and "actually coalesces in the terminal stages, to suggest an advanced state of measles." The mottling may spread over the abdomen, shoulders, and even the hollows inside the elbows. The labia minora become enlarged to about twice their normal size as tension increases, and turn a deeper, scarlet hue (purplish in a woman who has borne several children). The intensity of sexual response is directly proportional to this color change; in no observed case has a woman reached a deep-color phase without proceeding to a satisfactory orgasm. Engorgement of the labia minora and the outer third of the vagina creates an "orgasmic platform." ∙ORGASM. With the physiologic stage thus set, a woman should experience an orgasm even more intense than a man's and marked by strong contractions of the engorged pelvic structures. The contractions usually occur at one-second intervals, continue for three to four seconds and up to ten or twelve seconds of "agonized physical effort." ∙RESOLUTION. After an unusually intense orgasm, this phase may drop a woman into deep sleep within a minute or two. ("Postorgasmic sleep" had previously been regarded as a male characteristic.) The measles-like rash fades, the engorged vessels of the pelvis and breasts relax to permit the resumption of normal blood flow, and the vagina subsides into a state that facilitates the movement of sperm to ovum for conception.
The Lethal Vagina. A major controversy in female physiology has concerned the source of the all-important vaginal lubricant. Some authorities have traced it to the uterine cervix; others, to the Bartholin glands flanking the vagina. In fact, says Dr. Masters, the normal cervix secretes nothing of any importance; the Bartholin glands secrete only a minute quantity of lubricant. According to Dr. Masters, the vaginal walls themselves supply nearly all the vaginal lubricant. How they do so is unclear, since there are no glands in the vaginal walls, and this is a subject of continuing study.