"We are told that this age is one of nervous strain. Probably in their own time the monsters of cretaceous days would have expressed a similar opinion, had the opportunity been granted them. From the beginning, the outer world has modified all animals possessed of a nervous system mainly by its aid, and as far as this system could alter its reactions, just so far could the animal adapt itself to the changed environment. In this generation, to be sure, our cephalic centres are sometimes overworked, whereas in the remote past the stress fell more on other parts; but we are rather allied to the rock-bound dead by an inherited power to respond than separated from them by a recent capacity for nerve exhaustion. As the reader will perceive, these remarks might serve to magnify the office of this book by suggesting how fundamental to the welfare of all higher animals are the powers of the nervous system, and therefore how important it will be to search out the growth changes which produce them. It seemed desirable to bring together in a comprehensive way the facts bearing on this portion of the problem. In discussions upon growth, the valuable records on brain-weight are sometimes alone brought forward, but there exist a vast number of other facts, which, when joined with these, illuminate not only them, but the entire field of view, and indicate the unworked areas within it. I have therefore sought especially to emphasise some more neglected points. Let me enumerate a few: the growth of the nervous system compared with that of the body; the interpretation of brain-weight in terms of cell structure; the early limitation of the number of nerve cells; the peculiar relation in this system between increase in size and in organisation; the large though variable number of cells which have but slight importance in the final structure; the dominance of nutritive conditions; the wide diffusion of nerve impulses; the incompleteness of repose; the reflex nature of all responses; the native character of mental powers; and the comparative insignificance of formal education"--Preface. (PsycINFO Database Record (c) 2010 APA, all rights reserved).