INTRODUCTION 



In planning a series of text-books for elementary 

 school use I have borne in mind the fact that the main 

 object of physiological instruction should be to aid in 

 the establishment of good hygienic habits. I have also 

 remembered that habits are more often established in 

 the individual by social custom and wont, by example 

 and precept, than by logic and reason. 



It is recognized that mere knowledge of an intellec- 

 tual character is ineffective. We all know much better 

 than we do. Only that knowledge is effective which is 

 related to doing, knowledge which we actually put 

 into practice. The effect of knowledge upon action is 

 an important, even if not the ultimate, criterion of its 

 value. It is relatively useless to teach children about 

 the body, unless the teaching is done in such a way as 

 to lead them to desire to form their lives accordingly. 



The purpose of this series, then, is to introduce that 

 atmosphere, both of intellectual comprehension and of 

 social custom, which shall result in the unconscious as 

 well as the conscious development of wholesome hygienic 

 habits. In order to so arrest the attention that convic- 

 tion may follow and right habits be started, I have 



