Bonk: The Curious Coupling Of Science And Sex

Even the language of anatomy imbues the organ with an innlike hospitality, the entrance to the structure being named the “vaginal vestibule.” Take off your coat and stay awhile. Gynecologist Robert Latou Dickinson, circa 1910, documented its wondrously accommodating nature, using his fingers as a measuring tool. The volume of the virgin vagina is “one finger”; the married woman rates “two full fingers.” Once the babies start coming, it’s “three fingers” and up, all the way to Subject No. 163, whose vestibule (and parlor) appear in a pen-and-ink rendering in Dickinson’s Atlas of Human Sex Anatomy with the doctor’s entire hand submerged

The spinal reflex known as the Lazarus sign has been spooking doctors for centuries. If you trigger the right spot on the spinal cord of a freshly dead body or a beating-heart cadaver—meaning someone brain-dead but breathing via a respirator, pending the removal of organs for transplant—it will stretch out its arms and then raise them up and cross them over its chest.

electronics term for circuitry mix-ups is crosstalk: a signal traveling along one circuit strays from its appointed route and creates an unexpected effect along a neighboring circuit. Crosstalk explains the faint voices from someone else’s conversation in the background of a telephone call. Crosstalk in the human nervous system explains not only the man who enjoyed his toilette, but also why heart attack pain is sometimes felt in the arm, and why the sensations of childbirth have been known to include orgasmic feelings or, rarely, an urge to defecate. Orgasms from nursing (or nipple foreplay) are another example of crosstalk. The same group of neurons in the brain receive sensory input both from the nipples and the genitals. They’re the feel-good neurons: the ones involved in the secretion of oxytocin, the “joy hormone.” (Oxytocin is involved in both orgasm and the milk-letdown reflex in nursing mothers.)

Penile thrusting on its own—with no foreplay or during-play—is, concluded Alzate, “an inefficient method of inducing female orgasm.”

No one had expected this, possibly because their inner cousins expand so much. The labia minora enlarge by two or three times their normal diameter. They also, as both Masters and Dickinson observed, change color, turning pink, bright red, or, occasionally, in women who’ve given birth, a deep wine color. In all of the 7,500 female sexual response cycles that Masters and Johnson watched, no woman who had an orgasm failed to display this “florid coloration” just beforehand. If a man wants to know whether a woman is faking her orgasms he could, barring some logistical hurdles, look for this “sex-skin reaction.” Which, by the way, is not to be confused with the “sex flush” (red blotches that may appear on a woman’s chest when she’s aroused). And the “sex flush,” in turn, has nothing to do with the “urge to void during or immediately after intercourse.”

Here’s something else no one but Masters had noticed. The clitoris hides at a certain point in the proceedings. In the stage of arousal just before orgasm, the visible portion of the clitoris retracts under its tiny foreskin. It disappears from view, potentially creating great confusion and consternation on the part of the person doing the stimulating.

For example, did you know that “defecating” can briefly bring your heart rate down by eight beats per minute?