The Book of Household Management by Mrs. Beeton

53. IN GIVING A LETTER OF INTRODUCTION, it should always be handed to

your friend, unsealed. Courtesy dictates this, as the person whom you are introducing would, perhaps, wish to know in what manner he or she was spoken of. Should you _receive_ a letter from a friend, introducing to you any person known to and esteemed by the writer, the letter should be immediately acknowledged, and your willingness expressed to do all in your power to carry out his or her wishes.