THE NOTION that Catherine de Medici singlehandedly transported Italian cooking to France when she married Henry II in 1533 is nonsense according to Leonard Beck, a curator of rare books in the Library of Congress. "Italian cooking was already in France in 1505, when Bartolomeo Platina's cookbook was translated into French," Beck said. Beck suspects that Catherine, who made tours all over France to become acquainted with the country, may have been responsible for refining French manners because she and her ladies-in-waiting ate at court. Prior to that few women ate with the men.

Sitting in the Library's rare-book room, Beck expanded on his theory. "There is no such thing as French cooking. There was a Mediterranean style of cooking carried around by the 14th-century 'Jet set.' The professional cooks in the courts were trying to outdazzle each other. These people lived far above everyone else, so what is found in these early cookbooks has no relation to what other people ate.

"The same dishes," he said, "appear over and over again in different countries.

"The word 'daube,' which 20th-century cooks connect with the French dish daube de boeuf , existed in English in 1390 and can be found in 16th-century Spanish and Italian cookbooks," Beck said.

"You can find blancmange in Italian, Spanish, even German in the 15th century. Most people think of it as French."

Beck bases his theory on an extensive knowledge of the contents of what he says is the "best collection" of rare books in the United States. Behind a heavy, gray metal door, up in the stacks above the rare-book room are stored the culinary secrets of that 14th-century "Jet Set" . . . among others. A jet set that traveled at a trot, to be sure, but nevertheless royalty and nobility who married across national boundaries, carrying their cooking traditions with them.

Beck's theory is that the culinary world of what is now called Western Europe knew no boundaries. Beck has almost 5,000 cookbooks from which to draw his information: the 4,350-volume Katherine Golden Bitting collection on gastronomy and approximately 400 books that were given to the Library by Elizabeth Robins Pennell.

The first cookbook was not a book at all but a manuscript, a 9th-century work attributed to someone called Apicius, who, as Beck has written, "may have been three people and who like Joe Miller did not write the book for which he ever will be known."

The first printed cookbook, part of the Bitting collection, appeared in 1475: Platina's De honesta voluptate . Platina, the pope's librarian, acknowledged his indebtedness for the material to a manuscript written between 1450 and 1460 by Maestro Martino. The first French cookery manuscript, by Taillevent, whose name is enshrined in a three-star Paris restaurant, was written in 1390. It was printed in 1490.

The first English cookery manuscript also appeared in 1390. And the first American cookbook, printed in Williamsburg in 1742, was originally published in England.

When English cookbooks were published in the United States, some American recipes were slipped in. Both the 1805 and 1812 American editions of the well-known English cookbook by Hannah Glasse, published in Alexandria, Va., contain recipes not only for johnny cake and Indian pudding, but for moonshine.

Beck believes that "cookbooks integrate cultural history." If you read your way through them you will know not only about what the rich ate from the 15th century on; you will know about their manners, their health, their daily lives, even their politics.

The character of French cuisine during the time of Louis XIV and Napoleon, Beck said, reflects the style of the periods. Careme, one of the foremost chefs in history, "had delusions of grandeur like Napoleon. At the same time there was an ordering. Everything was controlled: They carefully laid out Versailles in sugar paste." It was the height of the piece montee , and elaborate table decoration laid out like an architectural rendering and not unlike the formal gardens.

A 16th-century Italian cookbood discusses "meat Hebrew style," which Beck thinks means kosher meat. He finds this recipe a fascinating example of "something very specific happening" and probably indicative of interaction among Jews in Italy and the upper classes, because "these books for cooking are for dignitaries." This is contrary to accepted theory that all Jews in Italy lived in the ghetto.

One recipe in an English cookbook published in America in 1792 offers several morsels of the information a food historian cherishes. "To dress haddock the Spanish Way use garlick, sweet oil and love apples . . . " This shows that the influence of Spanish cooking not only reached England, but made its way to the United States as well. Contrary to accepted theory, garlic and sweet oil (presumably olive oil) were not exotic items. And recipes using love apples (tomatoes) existed here during the time when many people are supposed to have thought they were poisonous.

By the 18th century, especially in England, Beck says, "there was a flood of cookbooks, a manifestation of the drive for self-improvement, for a better life." These books were no longer just for professional cooks or ladies of the manor. "They were for what will be the middle class after the Industrial Revolution. It's as if England were getting ready for the Empire," Beck speculated.

Cookbooks, Beck explained, come out of medical books and farm books. So until the middle of the 19th century they dealt not only with recipes, but with the running of farms and households, the brewing of medicinal potions for the family, table manners and table settings.

The move away from compendiums of household information toward recipes-only books has now come full circle. Cookbooks once again combine recipes with information about health or nutrition. The idea goes back to the 2nd century. Galen the physician may have been the first to expound the theory that you are what you eat. He believed that if a person is sick, it is his fault; that it is not a form of revenge by the gods but usually caused by abuse of the person's diet.

The same message is found in another book in the Bitting collection, Regimen Sanitatis Salernitanum . "Man's health is man's responsibility. Man's proper concern is care, not cure," it says.

In 1709, Dr. Hecquet, dean of the faculty of medicine in Paris, wrote that the abstinence practiced during Lent was actually good for people because it kept them away from rich foods. He said his rich patients were overfed. Hecquet wrote that he went to the kitchen of his patients to kiss the cooks for having made him wealthy.