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?