Today business cards are distributed by working people of all social classes, illustrating not only the uniquity of commercial interests but also the fluidity of the world of trade. Whether one is buttonholing potential clients for a carpentry service, announcing one"s latest academic appointment, or "networking" with fellow executives, it is permissible to advertise one"s talents and availability by an outstretched hand and the statement "Here"s my card." As Robert Louis Stevenson once observed, everybody makes his living by selling something. Business cards facilitate this endeavor. It has not always been this way. The cards that we use today for commercial purposes are a vulgarization of the nineteenth-century social calling cards, an artifact with a quite different purpose. In the Gilded Age, possessing a calling card indicated not that you were interested in forming business relationships, but that your money was so old that you had no need to make a living. For the calling-card class, life was a continual round of social visits, and the protocol(礼遇) governing these visits was inextricably linked to the proper use of cards. Pick up any etiquette manual predating World War I, and you will find whole chapters devoted to such questions as whether a single gentleman may leave a card for a lady; when a lady must, and must not, turn down the edges of a card; and whether an unmarried girl of between fourteen and seventeen may carry more than six or less than thirteen cards in her purse in months beginning with a "J". The calling card system was especially cherished by those who made no distinction between manners and mere form, and its preciousness was well defined by Mrs. John Sherwood. Her 1887 manual called the card "the field mark and device" of civilization. The business version of the calling card came in around the mm of the century, when the formerly, well defined borders between the commercial and the personal realms were used widely, society mavens(内行) considered it unforgivable to fuse the two realms. Emily Post"s contemporary Lilian Eichler called it very poor taste to use business cards for social purposes, and as late as 1967 Amy Vanderbilt counseled that the merchant"s marker "may never double for social purposes".