PREFACE TO THE SECOND EDITION. 



Advantage has been taken of the necessity of issuing a second edition 

 of the American Text-Book of Physiology to alter somewhat its general 

 arrangement. The book has proved to be successful, and for the most part 

 has met only with kindly and encouraging criticisms from those who have 

 made use of it. Many teachers, however, have suggested that the size of 

 the book, when issued in a single volume, has constituted to some extent an 

 inconvenience when regarded from the standpoint of a student's text- book 

 that may be needed daily for consultation in the lecture-room or the labora- 

 tory. It has been thought best, therefore, to issue the present edition in two 

 volumes, with the hope that the book may thereby be made more serviceable 

 to those for whose aid it was especially written. 



This change in the appearance of the book has necessitated also some 

 alteration in the arrangement of the sections, the part upon the Physiology 

 of Nerve and Muscle being transferred to the second volume, so as to bring it 

 into its natural relations with the Physiology of the Central Nervous System. 



The actual amount of material in the book remains substantially the same 

 as in the first edition, although, naturally, very many changes have been 

 made. Even in the short time that has elapsed since the appearance of the 

 first edition there has been much progress in physiology, as the result of the 

 constant activity of experimenters in this and the related sciences in all parts 

 of the world, and an effort has been made by the various contributors to keep 

 pace with this progress. Statements and theories that have been shown to 

 be wrong or improbable have been eliminated, and the new facts discovered 

 and the newer points of view have been incorporated so far as possible. Such 

 changes are found scattered throughout the book. 



The only distinctly new matter that can be referred to specifically is found 

 in the section upon the Central Nervous System, and in a short section upon the 

 modern ideas and nomenclature of physical chemistry, with reference especially 

 to the processes of osmosis and diffusion. The section dealing with the < Vntral 

 Nervous System has been recast in large part, with the intention of making 

 it more suitable to the actual needs of medical students ; while a brief presen- 

 tation of some of the elementary conceptions of physical chemistry seems to 

 he necessary at the present time, owing to the large part that these views are 

 taking in current discussions in physiological and medical literature. 



The index has been revised thoroughly and considerably amplified, a table 

 of contents has been added to each volume, and numerous new figures have 

 been introduced. 



August. 1900. 



