VI PREFACE 



and rearranged so as to incorporate the recent work on the effects of 

 deficiency oi; oxygen on the respiratory center, as well as the interesting 

 and important clinical applications of the subject. Several new chapters 

 have been added dealing with such practical problems as the measure- 

 ment of the functional capacity of the heart, the principles of ventilation 

 and the therapeutic value of oxygen, and the chapters on vitamines, on 

 the capillary circulation, on surgical shock, and on the interpretation of 

 polysphygmograms have been rewritten. 



In practically every other section of the book many additions have 

 been made, particularly in that which deals with the endocrine organs, 

 and several new figures and tables have been added. To make room for 

 these changes some of the more technical details, appearing in the pre- 

 vious editions, have been put in small print and some of the figures 

 removed. This has been done in order to keep the volume as near to its 

 original bulk as possible. 



I wish to take this opportunity to thank my colleagues here and else- 

 where for many valuable suggestions and for their encouraging com- 

 ments on the book. I am also greatly indebted to Dr. N. B. Taylor for 

 his assistance in the preparation of this edition and for reading the proofs. 



J. J. E. MACLEOD. 



Toronto, Canada, 

 1920. 



PREFACE TO FIRST EDITION 



The necessity of allotting the various subjects of the medical curric- 

 ulum to different periods, so that the more strictly scientific subjects 

 are completed in the earlier years, has the great disadvantage that the 

 student, being no longer in touch with laboratory work, fails to employ 

 the scientific knowledge with full advantage in the solution of his clin- 

 ical problems. He is apt to regard the first two or three years in the 

 laboratory departments as inconsequential in comparison with the sup- 

 posedly more practical instruction offered during the subsequent clinical 

 years. He is taught by his laboratory instructors to observe accurately, 

 and to correlate the observed facts, so that he may be enabled to draw 

 conclusions as to the manner of working of the various functions of the 

 animal body in health, and before proceeding to his clinical studies, he 

 is required to show a proficiency in scientific knowledge, because it is 

 recognized that this must serve as the basis upon which his knowledge 

 of disease is to be built. When the clinic is reached, however, the meth- 

 ods of the scientist are not infrequently cast aside and an understanding 



