P E E F A O E. 



IN entering upon the labor incident to the preparation 

 of a work purporting to treat comprehensively of the physi- 

 ology of man, the author appreciated the magnitude of the 

 undertaking ; and the special study which it necessarily de- 

 manded has not diminished that diffidence with which a 

 student of any of the natural sciences puts forward a book 

 which he hopes may add somewhat to existing knowledge, 

 or fairly represent what is known in any particular depart- 

 ment. In assuming so grave a responsibility, the author 

 should be actuated by a sense of peculiar fitness for his task, 

 as well as a -conviction that literature demands such a work 

 as he proposes to write. Without assuming these good and 

 sufficient reasons, the author of the present volume pleads an 

 earnest desire to advance the science of physiology and facili- 

 tate its study ; and he indulges the hope that he may be in- 

 strumental in making the student and practitioner of medi- 

 cine better acquainted with what must be conceded to be the 

 basis of true pathology, and interest, to some extent, the gen- 

 eral reader in the all-important subject of human physiology. 



The plan of the present work involves a consideration of 



