PLAN OF THE BOOK vii 



how they are eliminated from the body. This com- 

 pletes the story of the foods, which is told in the first 

 twelve chapters. 



Bones and muscles are next discussed, to learn how 

 some of the energy of the foods is used in moving any 

 part of the body and in locomotion. These two topics 

 must be studied together so as to bring out the fact 

 that the bones serve as levers for the muscles, and 

 hence such activities as standing, walking, running, 

 swimming, breathing, talking, etc., are made possible. 



Next follows a study of the nervous system and the 

 special senses, to see how all the processes and activities 

 of the human body are controlled and unified. This 

 furnishes an opportunity to review all the other systems 

 and at the same time to study them in a new light. The 

 last three chapters treat bacteria and diseases, general 

 sanitation, and accidents and emergencies respectively. 



Hygiene. The central thought of the entire book is 

 personal hygiene and public health. Such facts of 

 structure are taught as are necessary to enable the 

 pupil to understand the laws of health. Hygiene will 

 be dogmatic and uninteresting if one does not know 

 how an organ or a system works, and a knowledge of 

 function demands a certain amount of anatomy. It is a 

 mistake to attempt to teach hygiene without the neces- 

 sary background of physiology and anatomy. For that 

 reason the subject of hygiene is considered in connec- 

 tion with each topic discussed and generally in the 

 same chapter, but there are several chapters devoted 

 wholly to hygiene. 



