PARIS — THE French may feel shaky about the underpinnings of the economy. But about the underpinnings for the body, they are as rock solid as the Arc de Triomphe.

During a summer when the French are drooping, the best uplift can be found in the Louvre complex at the Museum of Decorative Arts, which has mounted a dazzling exhibition on undergarments and embellishments dating from the 14th century on: corsets and bustles, hoops and push-up bras, crinolines and codpieces. The exhibit, titled “Behind the Seams, the Mechanics of Underwear: An Indiscreet History of the Silhouette,” provides a fascinating contrast between the industrial-seeming tools used to shape the body and the sexiness that results.

Only a French museum would take fine washables so seriously. The word lingerie, after all, derives from the French word linge, meaning “washables.”Seismic social changes have always been reflected in fashion, and the politics of lingerie can be incendiary. Consider recent reports about Ritu Tawade, a city official in Mumbai who has responded to the horrific rapes in India by crusading to remove lingerie-clad mannequins from store windows, fearing they incite rape.

It was only two years ago that Saudi Arabia, hypocritical home to many racy lingerie stores, compelled them all to employ women instead of men.

In “The Heat,” Melissa McCarthy’s Boston cop warns Sandra Bullock’s F.B.I. agent that her Spanx squish internal organs. It’s the same argument a bloomer brigade of feminist reformers used in the belle époque to denounce corsets — stays that stayed around for 500 years.

Jean Cocteau wrote amusingly in 1913 about the women at Maxim’s: “It was an accumulation of velvet, lace, ribbons, diamonds and what else I couldn’t describe. To undress one of these women is like an outing that calls for three weeks advance notice, it’s like moving house.”Denis Bruna, the curator of the exhibit, said he has studied the human form in art through the centuries and has read countless ancient texts instructing women to be beautiful and men to be virile. He even tried on the intimate items from the time of the ancien régime.

“It feels good,” the 45-year-old said in French with a droll smile. “It makes you stand up very straight. You feel noble.”He explained that the hard corsets were mostly worn by aristocratic women who wilted standing at court all day and needed bracing. If you were rich and had servants, you could have stays laced in the back (in the squeezing-the-breath-out-to-get-back-an-18-inch-waist style of Mammy and Scarlett O’Hara). Lower-class women had their stays in the front, so they could lace them on their own.

As though women weren’t trussed up enough, the rigidity was accentuated by a busk, a concave piece of metal, horn or whalebone that was inserted into the front of the corset to hold the torso erect. Sometimes these busks had portraits or love messages engraved on them.

The most wince-worthy displays: iron medical corsets from the 16th century for correcting curved spines; miniature corsets worn by infants and toddlers, because physicians of yore insisted that children’s soft bodies needed support; and corsets for pregnant and nursing women (the latter with little shutters).

The Marie Antoinette “grand habit” silhouette, with the wasp-waist corsets often made from bone at the roof of the whale’s mouth, and 12-foot-wide paniers at the hips were so broad that the side cages had to be retractable by hand so the ladies could get through a door. Was this why French doors came into fashion? Picture them all crashing into one another at court.

The paniers were balanced by pouf hairdos, built on a scaffolding of horsehair and wire, covered with powder and topped with toy sculptures like a little farm or a battleship.

“The lower parts of the woman’s body were less noble, so they were hidden,” Bruna said. “They thought the legs were ugly and sheathed them in pantaloons. The shape represented a pedestal base to make the top prettier.”Finally, in the World War I era, Coco Chanel began helping women come into their own, unstrapping them from their hourglass constrictions and sheathing them in supple jersey. Maybe that’s why you see Chanel’s image here more often than Joan of Arc’s.

Yesterday’s aristocratic underwear morphs into today’s fetishistic outerwear. The show illustrates the influence of the ancient fashion on modern designers, including a Vivienne Westwood bustle frock and an Alexander McQueen corset dress.

Mirabile dictu, there are even new variations on Renaissance codpieces, or braguettes, a bragging-rights style bound to disappoint. “They’re already being sold in gay shops in France and on the Internet,” Bruna said.

It was commonly thought that the point of lingerie was to incite the lust of men. Yet, as this exhibit shows, women have also used underwear to assert their power and status.

As we celebrate Bastille Day, note this: The mannequins wearing the aristocratic undies have no heads.