This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables. A SIGN is a distinctive mark used in order that something may be recognized or that its presence may be known. The letters of the alphabet are signs of certain sounds. A sign once established actually suggests the thing it stands for, with or without reason, intention or choice. An emblem has some natural fitness to suggest that for which it stands. (An emblem resembles in some respect the thing it stands for.) A symbol is a term given to an object representing to the mind something that is not shown but that is realized by association. A symbol is a term chosen to suggest something else. (A symbol represents with or without natural fitness; letters are often used as symbols in the sciences.) A symbol may also be an emblem, and when such is the case it is doubly appropriate for the use in question, in the present case,