It is important at the outset to understand just what memory is and what is aimed at in its development, for unless we know where we are going, we shall be like the man in the song, I don't know Where I'm going, but I'm on my way. A very good definition of memory is the one given by the Century Dictionary: The mental capacity of retaining unconscious traces of conscious impressions or states, and Of recalling these traces to consciousness with the attendant perception that they (or their Objects) have a certain relation to the past.