EducT 839.161678 NARVARD COLLEGE LIZCARY BY EXCHANGE FROM COPYRIGHT, 1912, BY THE MACMILLAN COMPANY. Set up and electrotyped. Published February 1913. Reprinted TO THE MEMORY OF MARTHA FREEMAN GODDARD WHOSE DEVOTED INSTRUCTION IN BIOLOGY IS A LASTING INFLUENCE FOR GOOD IN THE LIVES OF HUNDREDS OF BOYS AND GIRLS AND WHOSE RARE SKILL IN LEADERSHIP IS AN INSPIRATION TO EVERY TEACHER WHO KNEW HER THIS BOOK IS DEDICATED BY THE AUTHORS PREFACE ALL the activities of a plant, of an animal, or of man may be grouped in three classes. One class embraces the functions relating to the life of the individual organism. These functions have to do with the processes of eating, digesting, assimilating, taking in of oxygen, producing of energy, and excreting of waste matters. These may be called the nutritive functions, if the term is used in its broadest sense. To the second group of activities belong the functions that have to do with the perpetuation of the animal or plant species, and these are known as the reproductive functions. Living organisms, whether plant, animal, or human, may, in the third place, be considered in their relations to one another and especially to the general welfare of mankind. Thus we may discuss the beneficial or injurious effects, so far as man is concerned, of different kinds of insects or of various types of bacteria; we may learn of the activities of individual men or of groups of individuals which promote or retard the advance of human society; or we might, if we were to carry the study still farther, even seek to learn the ways by which the higher thoughts of mankind, as expressed in poetry, music, and religion, affect the development of the human race. In the preparation of this text, the authors have sought to keep continually in mind these three classes of activities, and to unify the study of plant, animal, and human biology by choosing those topics for laboratory work or text description that have to do in a broad sense with one or the other of the three great groups of functions of living things to which we have just referred. In doing this, they are conscious that many subjects have been slighted or altogether omitted which might well be treated in a year's work in either botany, or zoology, or human physiology. Again, in the treatment of a given subject, for example, stems, fishes, or circulation, special emphasis might be laid on structure, on function, or on the relation of the given topic to human life. Books both interesting and scientifically worth while could be prepared along any one of these lines, or, if time permitted, all three phases might be equally emphasized. But when we remember that less than two hundred school periods will probably be devoted by the average student to the study of biology, the necessity for adhering pretty consistently to some one plan is obvious. In the judgment of the authors the kind of biology most worth while for the average boy or girl of fourteen years of age is not one based primarily on structure. Young students are naturally more interested in activities or functions than they are in mere form or structure. Hence, if we wish to work with, rather than "against the grain," we must put function in the foreground of our discussion. Every boy and girl knows, too, that both plants and animals as well as human beings must have food and drink, and that they grow and reproduce their kind. It is relatively much easier, therefore, to unify a course like this along physiological lines than on the basis of morphology, or of homologies of structure, many of which are far too complicated to be made clear to young students. If properly outlined and presented, there is probably no subject in the school curriculum that can be made of more service to a growing youth than can biology. Biological problems confront him at every turn, and if he is a normal being, he will have asked himself question after question |