The term temperament is used in this paper to denote the sum total of inherent emotional potentialities and kinetic tendencies peculiar to the individual. A person's tendencies to action and reaction, his outlook upon life, and his liability to mental and nervous disorder, are in a large measure determined by the temperament with which he is born. Character, in the usual sense of the term, and personality, at any given time, are the resultant of temperament and environment in its widest sense, past and present, and previous reactions thereto, and are varying quantities. Temperament, although susceptible of modification by external influences, cannot be changed fundamentally in type.