PREFACE 



Yale University did me the great honour of inviting 

 me to deliver the Silliman Lectures for 1915. Owing 

 to the war I was unable to give the lectures in the ap- 

 pointed year ; and I must first of all thank the Univer- 

 sity for permitting me to postpone them till the present 

 time. 



The subject of the full lectures, as they will, I hope, 

 before long appear in book form under the imprint of 

 the Yale University Press, is the Physiology of Breath- 

 ing. Much of the material contained in them is, how- 

 ever, of a technical character, hardly suited for public 

 lectures. With the approval of the President, I have 

 therefore delivered the following four public lectures 

 confined to points of more general interest, the nature 

 of which is indicated by the title. 



JOHN SCOTT HALDANE. 

 New Haven, October, 1916. 



