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which an elementary knowledge of biology ought to help him to answer. Some of these questions may be the following: Whence comes the food and oxygen supply used by man? Why are food and oxygen needed in our bodies? Why are some substances beneficial to the body and others injurious? What is the cause of disease, and how is disease transmitted? And if we were to tabulate the biological questions that occur spontaneously to the average pupil in the first year in the high school, we should doubtless find that a great proportion of these questions had to do with the relation of the living world to human life. Is it not clear, therefore, if we are to outline a course in biology that will best fit the interests of the "live material," i.e. the boy or girl who is to take the course, that the central idea or factor must be man; that all the various functions considered must have some relation to human life; and that the course, to be of practical importance, must suggest to the youth better ways of carrying on his own life and of helping to improve the surroundings in which he lives?

In order, however, to treat intelligently such a function, for example, as respiration or digestion, it is of course necessary to know something of the machinery by which each of these processes is carried on, and so there must be at least a minimum consideration of the structure of plants, animals, and the human body. In every case, however, the authors have called attention only to those details which seem to be absolutely essential for an interpretation of the function under consideration. Whenever names in common use are sufficiently accurate for descriptions, these are chosen in preference to scientific terms. Frequently the latter are necessarily used, and so, whenever their meaning is made clearer by referring to their derivation from Latin or Greek, these derivations are indicated in parentheses.

The sections in coarse type contain the material that seems to the authors most essential for any clear understanding of the subject as a whole, while in fine type we have put additional laboratory work and text description which we believe to have an important bearing on the various topics discussed. If both coarse and fine print on animal, or plant, or human biology are used, sufficient material for a half-year course in either elementary botany, zoölogy, or human physiology will be provided.

In the judgment of the authors, plant biology should always be considered first and human biology last in the course for the following reasons: (1) Plants lend themselves far more readily to close observation and especially to experiments than do animals, and so fundamental processes which apply to all living things can be demonstrated scientifically from plant material. (2) Plants are the final source of all the food supply of animals and man, and if the composition and manufacture of the nutrients are taught early in the course, a solid foundation is laid for all subsequent study of nutrition in animals and man. (3) The purpose of the animal study is largely that of showing the adaptations of animal structure to functions and the relations of the animals studied to human welfare. (4) And finally, if human biology comes last in the course, it may be presented in such a way as to review, sum up, and give real significance to many of the facts learned earlier in the course. In fact, as the work proceeds, comparisons will constantly be made between plants, animals, and man to show that the essential differences in the three kinds of organisms consist not in the differences in the functions which they carry on, but in the organs by which the functions are performed.

So far as the order of individual topics under plant, animal, and human biology is concerned, the instructor should

plan the sequence that best fits the season. In fact, the last use that a good teacher will make of any laboratory manual or text-book is that of following it slavishly. It is the hope of the authors, however, that the laboratory guides and the text descriptions which follow may be sufficiently suggestive to help some teachers to work out improved methods in biological instruction. In Appendix II will be found a suggested order of topics which the authors have found satisfactory.

Living organisms are to a large extent to be regarded as chemical engines so constructed as to liberate different kinds of energy. No one, of course, knows in any ultimate sense how even the simplest functions are performed by the simplest animals or plants. But it is utterly useless to attempt to teach biological functions without first presenting some of the elementary principles involved in physical and chemical phenomena. For this reason the first chapter in Plant Biology is devoted to the study of the Composition of Lifeless and Living Things. In Chapter III is a brief discussion of the structure of a common plant, and since cells are fundamentally alike in structure and functions in all living organisms, emphasis is laid early in the course on the essential characteristics of these cellular elements in plants. Another topic which necessarily recurs throughout plant, animal, and human biology is the principle of osmosis and its applications. The authors have inserted experiments which in their experience have helped to fix in mind this important principle and which demonstrate the necessity of digestion in plants and animals.

After this brief consideration of the fundamentals of plant composition, structure, and processes, Chapters V, VI, and VII are devoted to the study of the adaptations of plants for performing nutritive and reproductive functions. In

Chapter VIII are grouped experiments and descriptions the aim of which is to show various ways in which plants are propagated. This treatment presents only the briefest statement of underlying principles, since any extended discussion of this topic belongs to a course in agriculture.

In Chapters IX (Plants in their Relation to Human Welfare) and X (Plant Classification) the method of presentation is strikingly different from that adopted in the rest of the book, particularly so in the treatment of the spore-bearing plants. The authors believe that every pupil should be taught something of these simpler forms (especially bacteria), and that he should get as many of these facts as possible by observation. But to expect much laboratory work from young students on difficult microscopic forms like many of these cryptogams, is, we are confident, quite out of the question. We have, therefore, frankly abandoned the inductive method of study and have suggested that the laboratory work be largely in the nature of demonstrations. It is, of course, understood that if these forms are studied, the drawings and descriptions will be prepared from material in the hands of the student.

In our judgment there are few if any biological topics which are more important in their practical bearings than is that of bacteria. As commonly studied the disease-producing effects of these organisms are emphasized so much that boys and girls do not appreciate that all the work of the higher plants depends ultimately upon the activity of these low forms of fungi. In order to bring out this aspect of the work of bacteria and for other obvious reasons the structure, physiology, and economic benefit of these organisms are considered in the chapter on the relation of plants to human welfare, while their pathogenic effects are reserved for discussion in human biology.

The method of presentation in "Animal Biology" is somewhat different from that employed in "Plant Biology," for the reason that several widely different types of animals are studied. Limitations of time compel a rigid and somewhat narrow selection of groups for intensive study, and only those functions of each animal are considered which have some relation to human biology, or which have a broad, economic bearing. Thus insects are discussed largely because of their injurious or beneficial effects upon mankind; birds and fishes, because of their economic importance, and because of the great need for their conservation; and one-celled animals because of the light they throw on cellular processes. Certain other somewhat less important topics are considered incidentally'; for example, protective resemblance and metamorphosis among insects, and the striking adaptations of structure to function in the bills, feet, and feathers of birds.

The animals suggested for additional study, if time permits, are representative mammals, reptiles, amphibia, arthropods, molluscs, worms, and cœlenterates. In many classes there are students who can work faster than the others, or who are interested in pursuing further their biological studies. Such students may be directed in carrying on some of these studies either in class or outside of school hours. In any case, students are likely to acquire considerable information by reading these textbook descriptions and studying the illustrations.

All the work of the year should lead up to and culminate in human biology. Here, too, however, many important topics must be treated only superficially, or altogether omitted, on account of lack of time. The authors believe that in this, the most important part of the course, practical hygiene should be taught as effectively as possible, and that the necessity for good food, pure air, varied exercise, and suffi

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