PREFACE 



The present book is a reprint of the physiological por- 

 tion of our larger work entitled The Human Mechanism, 

 together with Chapter XVI (Drugs, Alcohol, and Tobacco), 

 which has been added to meet the requirements of law 

 in some states with regard to the teaching of physiology. 

 For those who desire in compact form the elements of 

 physiology as a part of general biological training, as an 

 introduction to the study of psychology, or for other spe- 

 cial purposes, and for those who, having undertaken the 

 study of hygiene and sanitation in Elements of Hygiene 

 and Sanitation (Part II of The Human Mechanism), desire 

 to acquaint themselves more fully with the fundamental 

 physiology, the present volume should prove useful. 



The references to Part II have been retained in the text, 

 and apply either to The Human Mechanism or to Elements 

 of Hygiene and Sanitation. 



