6 PLAN AND PURPOSE OF THIS BOOK 



What is true of chemistry is equally true of biological science. We 

 spend too much time in teaching uncsscntials taken from our 

 immense field, and we do not spend enough time in emphasizing 

 from constantlj- varied points of attack the fundamental truths on 

 which the science of biology is built. The pages which follow are 

 an attempt to drive home by repetition, and from many points 

 of view, some of the important principles of physiological biology. 



One sufficient reason for the placing of a course in biology in the 

 first year of the secondary course lies in the fact that at this time 

 the child is receptive to the message of applied biology. Private 

 and public hygiene, the message of protective medicine and san- 

 itation, the story of pure milk and of pure water and what they 

 mean to a community ; all these things can most logically be pre- 

 sented in a course that makes man the center. The allied topics 

 of conservation of plant and animal life, the destruction of harm- 

 ful plants and animals, the relation of insects and other animals to 

 the spread of disease, and the work of civic and government de- 

 partments in the development of nature's gifts and in the preser- 

 vation of national health should bo treated in their relation to 

 man. 



Moreover, the data given should be treated from the biological 

 standpoint, not that of botany, zoology, or human physiology. 

 Ideally, we might take up general principles and draw from the 

 great storehouses of plant, animal, and human biology to illustrate 

 each principle before going on to the next. Practically, however, 

 such a plan does not seem to be workable, partly because of the 

 difficulty of collecting enough material to make such demon- 

 strations possible. It is impracticable with immature students, 

 because they cannot grasp the many-sidedness of the application 

 at once. This will only come after repetition of the principle, each 

 time from a slightly different point of view. 



It frequently happens that the related study of plants and ani- 

 mals may be taken up to advantage. Insects and flowers, both 

 plentiful in the fall, may well be studied together for the relation 

 of life habits and adaptations in the insect to cross-pollination 

 of flowers. Applied biology, in its relation to plants or to animals, 

 must of course be treated from all sides. The fungi and the bac- 

 teria in their relations to man are conspicuous examples. 



