PREFACE TO THE REVISED EDITION 



This edition presents a thorough revision, in which the 

 authors have incorporated / those advances in physiology 

 which are directly applicable to the fundamental purpose 

 of this book as stated in the preface to the first edition. 

 Portions of certain chapters have been entirely rewritten, 

 notably those dealing with the work of organs and cells, 

 internal secretions, digestion, nutrition, and the central 

 nervous system. 



The advances of physiological knowledge in the past 

 decade have not only given clearer insight into the nature 

 of the processes which underlie the phenomena of living- 

 things but have also made the facts of physiology increas- 

 ingly helpful in the intelligent conduct of life. While this 

 latter point of view has chiefly determined the selection of 

 material to be included in this book, it has none the less 

 been necessary to lay the foundation for the understanding 

 of what we call the practical knowledge by a clear and suc- 

 cinct statement of the fundamental principles of physiology. 

 This first part of " The Human Mechanism " therefore serves 

 the purpose of those who cannot give the time necessary 

 for the more extensive study of physiology required of the 

 physician or the specialist in physiological science. 



It is hoped that the interest aroused in the applications 

 of physiology to the conduct of life may lead many readers of 

 this book to the subsequent study of hygiene and sanitation. 

 The second part of " The Human Mechanism" has therefore 

 been published under the title "Hygiene and Sanitation." 



We are indebted to Dr. E. P. Joslin for permission to 

 reproduce from his work on " The Treatment of Diabetes 

 Mellitus" the table on page 238. 



p iii 



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