PKEFACE 



No new facts are presented in this book. Rather has 

 an attempt been made to present simply from a physio- 

 logical standpoint the well-established facts of physiol- 

 ogy. To this end all details that might complicate the 

 matter have been omitted and a few general principles 

 have been emphasized. 



Human physiology is frequently presented in our 

 schools as an isolated subject unaffected by the laws of 

 other sciences. For this reason it fails to produce an 

 improvement in personal hygiene, and it fails to provide 

 mental discipline. To the young student then the 

 human body is apt to seem a unique development, its 

 structure and its functions unwarrantably complex and 

 its behavior quite independent of the ordinary laws 

 of nature. 



For four years in one of the best normal schools, the 

 author struggled with this mental attitude in pupils com- 

 ing from the lower schools. They seemed to have no 

 conception of cause and effect in connection with the 

 human body. The one idea most prevalent among them, 

 most antagonistic to the understanding of the principles 

 of hygieneand ; hysiology and most difficult to eradicate, 

 was the idea that things happen because the body needs 

 them to happen. That the operation of definite phys- 

 ical and chemical laws might have an effect upon the 



