Most rules are elastic and contract and expand according to circumstances.
You do not remind Mrs. Smith of having met her before, but on meeting
again any one who was brought to your own house, or one who showed you an
especial courtesy you instinctively say, "I am so glad to see you again."


=INCLUDING SOMEONE IN CONVERSATION WITHOUT AN INTRODUCTION=

On occasions it happens that in talking to one person you want to include
another in your conversation without making an introduction. For instance:
suppose you are talking to a seedsman and a friend joins you in your
garden. You greet your friend, and then include her by saying, "Mr. Smith
is suggesting that I dig up these cannas and put in delphiniums." Whether
your friend gives an opinion as to the change in color of your flower bed
or not, she has been made part of your conversation.

This same maneuver of evading an introduction is also resorted to when you
are not sure that an acquaintance will be agreeable to one or both of
those whom an accidental circumstance has brought together.


=INTRODUCTIONS UNNECESSARY=

You must never introduce people to each other in public places unless you
are certain beyond a doubt that the introduction will be agreeable to
both. You cannot commit a greater social blunder than to introduce, to a
person of position, some one she does not care to know, especially on
shipboard, in hotels, or in other very small, rather public, communities
where people are so closely thrown together that it is correspondingly
difficult to avoid undesirable acquaintances who have been given the wedge