PREFACE TO THE FIRST EDITION 



To set fixed limits to the subject matter of physiology is a very difficult 

 task, because, properly conceived,, large portions of the entire group of medical 

 and biological sciences belong to its province. A text-book designed primarily 

 for medical students can, however, regard the field as somewhat more re- 

 stricted; for the prospective physician has abundant opportunity to amplify 

 his knowledge of the bodily functions from his other studies. Hence in this 

 book I have followed the usual custom and have brought together only so 

 much of our information respecting the human body as can be described 

 as pertaining to its normal functions. The discoveries made in the realms 

 of practical medicine, of experimental pathology and of pharmacology, which 

 in many respects are so full of significance for the processes of the body, are, 

 therefore, for the most part passed by. In like manner the facts of compara- 

 tive physiology have been alluded to only in exceptional cases, since an ex- 

 haustive discussion of them would have increased the size of the book to a 

 not inconsiderable extent. 



For the same reason I have been unable to find a place for the short 

 histological discussion customary in text-books. I do not regard this as an 

 error, for a necessarily brief and superficial resume of the most important 

 histological facts could be of no great service, since the student needs a more 

 extensive knowledge of the finer structure of the body and must in any case 

 obtain this from the text-books devoted especially to that subject. I do not 

 therefore at all mistake the great importance of histology for physiology; 

 on the contrary, I would recommend that in the study of a text-book of 

 this science a text-book of histology (and one of anatomy) be always at hand 

 in order to combine the physiological facts with the histological and ana- 

 tomical facts. 



Physiological chemistry also has developed so far that more and more it 

 can claim the right to be regarded as an independent science. On the other 

 hand it is not possible to present the physiological facts without reference to 

 the chemical processes of the body. While therefore I am compelled to touch 

 upon the facts of physiological chemistry, I have limited the discussion to 



