The Science of Sex: Doing it for Science

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Doing it for Science

In the last issue it would publish in the twentieth century, the usually staid British Medical Journal printed a study that had doctors (and reporters) snickering from one end of Her Majesty’s realm to the other. Written by gynecologist Willebrord Schultz and his colleagues at the University Hospital in Groningen, Holland, the study addressed an ancient mystery: What actually happens during good old-fashioned, missionary-position sex? And it answered the question with a set of images that dragged pornography firmly into the high-tech era.


The problem with figuring out what happens during sex, of course, is that most of the action takes place deep within the woman’s pelvis. That hasn’t stopped inquiring minds from studying the issue, of course. In 1492 Leonardo da Vinci made a famous anatomical drawing titled Coition of a Hemisected Man and Woman, in which a copulating couple are represented as if they had been sliced down the middle with a band-saw. Of course, Leonardo didn’t really cut them in half, he just imagined it, and as a result the anatomical details are highly suspect. But for what it’s worth, Leonardo showed the man’s penis as sticking straight out from his body like a flagstaff.


Five hundred years later, the Dutch researchers decided to try and obtain real images of sexual intercourse by means of magnetic resonance imaging (MRI). It wasn’t easy. First, there was the question of space. If you have ever been inside an MRI machine you’ll know that it’s a tight fit: the tube you lie in is only twenty inches in diameter. Imagine having someone else in there with you, and then going through the contortions required for sex. The researchers had to select smallish volunteers, and in fact the first couple that succeeded in achieving penetration were amateur acrobats.


The researchers had an even more serious problem, though: the male volunteers’ penises did not stand up well to the high-stress conditions of the study. It took nearly a minute to acquire a single MRI image, and the men simply couldn’t keep their penises stationary and erect inside the woman’s vagina for that length of time.


Five years after the start of the study, however, two unexpected breakthroughs occurred. The researchers obtained a new MRI machine that could generate an image in a mere 12 seconds, and Viagra came onto the market. By swallowing one of the magic pills an hour before entering the machine, the men were able to maintain an erection as long as necessary. At last the researchers obtained sharp images of the man’s fully erect penis inside the woman’s vagina.


In these pictures, the penis is not straight but bent upward, with the hinge point near the abdomen. Thus the entire penis (including the root of the penis within the man’s body) has the curved shape of a boomerang. When a penis is erect, it’s pretty resistant to bending throughout most of its external

length, but does bend up and down fairly readily at its hinge, i.e. at the junction between the external and internal

portions of the shaft of the penis. This is why bending at this

point would not be particularly noticeable to a man during vaginal sex.


In the images, the sensitive lower surface of the penis presses against

the back wall of the woman’s vagina, an arrangement that may be highly stimulating to the man. Yet the penis makes little contact with the front wall of the vagina, which is the location of the controversial “G-spot.” This is the zone of heightened sensitivity that, in some women, triggers an orgasm that is different in kind from a clitoral orgasm. (The particular women who participated in the study said they did not have G-spots.)


The findings raise the question of whether other positions than the missionary position would provide better stimulation to the female partner. Sadly, most of the “Positions of the Day” featured on the Nerve home page could not be achieved inside any existing MRI machine. It seems likely however that rear-entry vaginal sex, as practiced by most non-human animals, would direct the penis toward the front wall of the vagina and would therefore provide better stimulation for women with G-spots.


The Dutch researchers also studied the anatomy of the woman’s pelvis during masturbation to orgasm. They found, as reported years ago by Masters and Johnson, that the uterus rises within the pelvis during the pre-orgasmic phase. They failed however to confirm Masters and Johnson’s report that the uterus doubles in size during sexual arousal — an improbable claim to begin with.


Although the information gathered in the Dutch study was hardly earth-shaking, it does open the door to future studies that could have a considerable impact on the way we have sex. With the introduction of larger and faster machines it may eventually be possible to obtain moving images not only of missionary-position sex but a variety of other positions, as well as oral and anal sex, fisting, penetration with dildoes and the like. Leonardo, thou shouldst be living at this hour!