PREFATORY NOTE TO THE AMERICAN EDITION. 



IT is no disparagement to the many excellent treatises on 

 Physiology, both at home and abroad, to say that, in some re- 

 spects, this one is better adapted for general use as a text-book. 

 It is compendious, and yet abounds in all the more recent views 

 and discoveries ; and it presents, in connection with Human 

 Physiology, a brief sketch of each function as it appears in the 

 lower orders. In tracing the progress from general to special 

 Physiology, Mr. Marshall has shown himself fully awake to the 

 requirements of the student, and has thus removed one of the 

 great difficulties in the comprehension of the subject. 



The additions of the American Editor are comparatively few, 

 and consist, mainly, of such materials as were, perhaps, not easily 

 accessible to the Author, or such as, in the judgment of the Editor, 

 might serve to render the text more intelligible to younger 

 students. These materials have been chiefly drawn from lectures 

 delivered in the University of Pennsylvania, and from experiments. 

 He desires to express his thanks to his friend, Dr. James Tyson, 

 for valuable assistance in preparing the manuscript for the press. 



1604 WALNUT STREET, 

 September, 1868. 



