Xll PREFACE TO THE FOURTH EDITION. 



View of the Functions of the Human Body" (CHAP, vi.), in which there 

 has been but little alteration. 



In conformity with the opinion expressed by some of his friendly 

 Critics, and by many Teachers of Physiology, the Author has reversed 

 the previous arrangement of the Chapters which treat of the Functions 

 in detail ; those relating to the Organic Functions being now placed 

 before those in which the Animal Functions are described, instead of 

 after. This has involved a new distribution of much of the matter 

 which was previously treated in a connected form in the Chapter on 

 the " Functions of the Nervous System;" since it has appeared to the 

 Author very desirable that the whole group of actions whose aggregate 

 makes up each function, should now be considered in its connection; and 

 thus the movements of Deglutition, Eespiration, &c., not having been 

 explained (as was formerly the case) in the earlier part of the volume, 

 are described, and their connection with the Nervous System examined, 

 under each separate head. As their general relations to the Nervous 

 System are previously explained, however, in the Sixth Chapter, the 

 Author does not apprehend that any inconvenience will be experienced 

 from this alteration. By the adoption of this change, in some degree 

 against his own judgment, the Author trusts that he has sufficiently 

 marked his desire to profit by all such advice as may be tendered to 

 him in a friendly spirit, and by those whose position or attainments 

 give value to their opinion. 



The series of Chapters on the several Organic Functions remain 

 essentially the same as in the previous Edition; but important additions 

 and corrections have been made in every one. Thus, in Chapter vii. 

 "On Food and the Digestive Process," the whole subject of Food is 

 much more fully discussed than heretofore ; and the most important of 

 the results obtained from the study of the Digestive Process by Fre- 

 richs, Bernard, and other experimenters, have been embodied in the 

 account of it. In Chapter vin., " On Absorption and Sanguification," 

 the structure and development of the Ductless Glands have been more 

 fully described, in accordance with the researches of Kblliker, Sanders, 

 Ecker, Gray, and others ; and their relation to the process of Sanguifi- 

 cation more clearly elucidated. In Chapter ix. " On the Circulation 

 of the Blood," the causes of the Heart's Sounds have been more fully 

 considered ; a view of the nature of its rhythmical contractions has 

 been suggested ( 498, 499), which the Author believes to be original ; 

 and the most important among the results of Prof. Volkmann's elabo- 

 rate researches on the Dynamics of the Movement of the Blood have 

 been introduced. In Chapter x., " On Respiration," the most import- 

 ant additions to the first section are those which embody the results of 



