PREFACE THE material in this book was first assembled for a professional crammer, who used it in preparing people for teachers' examinations and the like and as a quiz-compend for college students. In preparing it for the general reader I have rewritten the whole thing and omitted several of the more exasperating chapters. Long technical terms have been avoided as far as possible; but there is a limit to this sort of popularization, because the shorter a word is the oftener it is used, and the oftener it is used the less definite its meaning becomes. Popular language consists largely of very short words, and therefore-while it is an admirable medium for lying and trading and love-making-it is not adapted to the precise statement of scientific fact. Books of this type should be clear and concise at all costs, and they therefore are bound to contain some dogmatic assertions which must be modified in more pretentious works. To strew the pages of a book like this with qualifying phrases is to sacrifice both brevity and clarity and to gain nothing but a hypocritical air of scientific conservatism. Theoretical interests, too, must be sacrificed to pedagogical expediency. No one believes more firmly than I in the complete physico-chemical nature of all human behavior; but the mechanistic phraseology is still unintelligible to the average reader, and so I have not hesitated to use the teleological jargon of the vitalists. V. R. |