PREFACE Vil 



practical exercises that follow each chapter touch upon phases 

 of the subject not mentioned in the text and are therefore an 

 integral part of the work and not a mere review of the text. If 

 the student is encouraged to work out these exercises for 

 himself, it will be found .to advance his knowledge much more 

 satisfactorily than mere recitations about them. 



In arranging the chapters dealing with human physiology to 

 follow those concerned with the more fundamental principles of 

 all science, it has been possible to considerably reduce the 

 matter devoted to this subject without omitting anything 

 essential, since a large part of the usual high school course in 

 physiology is taken up with discussions of the physics and 

 chemistry of the bodily processes. If, however, it seems de- 

 sirable to have physiology precede the more general matter, 

 the student should be required to study carefully the other 

 sections of the book in which the laws underlying physiological 

 processes are treated at greater length. 



The matter in this book has been used by the author with 

 his classes in a large city high school for several years, and the 

 practicability of the course, and especially of the experiments, 

 has been tested under a variety of circumstances. In prepar- 

 ing the work for publication the author has had the advice and 

 assistance of several of his fellow-teachers to whom he takes 

 this opportunity of acknowledging his grateful appreciation. 

 That he has not always followed the advice so kindly and 

 cheerfully given will account for any errors that may be found 

 in the text. 



WILLARD N. CLTJTE. 

 JOLIET, ILLINOIS. 



