PREFACE 



When Yale University invited me to deliver the Silliman Lectures 

 for 191 5 I was asked to deal with the physiology of breathing 

 and include a general account of the long series of investigations 

 with which I had been associated on this subject and its practical 

 applications in clinical medicine and hygiene. Owing to the war I 

 was unable to give the lectures in 191 5, but in 191 6 delivered four 

 lectures which dealt only with some of the more general conclu- 

 sions to which I had been led, and were published early in 191 7 

 by the Yale University Press under the title ''Organism and 

 Environment as Illustrated by the Physiology of Breathing." 



The war has greatly delayed the appearance of the present 

 book, which treats the physiology of breathing fully in accordance 

 with the original plan. I have, however, abandoned the lecture 

 form, and what I had written four years ago has had to be largely 

 recast owing to the rapid advance of knowledge. The book is not 

 a mere compilation, but contains much that has never previously 

 been published, and is an attempt to give a coherent statement 

 and interpretation of what is known of the subject at present. I 

 fear that I may sometimes have unwittingly overlooked observa- 

 tions by others which would have added completeness to my 

 account. Yet I hope that what may have been lost in this way 

 will be made up for by the fact that the book embodies the results 

 of a continuous series of investigations leading to very definite 

 and consistent conclusions. 



About the middle piJast.ceatury the younger physiologists 

 broke away from the vitalistic traditions which had been handed 

 down to them, and set about to investigate living organisms 

 piece by piece, precisely as they would investigate the working 

 oTa complex mechanism. This method seemed to them to promise 

 success, and was popularized by such masters of clear and force- 

 ful expression as Huxley. It is still the orthodox method of physi- 

 ology, but the old confidence in it has steadily diminished in 

 proportion as exact experimental investigation has shown that the 

 various activities of a living organism cannot be interpreted in 

 isolation from one another, since organic regulation dominates 

 them. The keynote of this book is the organic regulation of 

 breathing and its associated phenomena. 



