x PREFACE. 
of late attained so great an extent and importance as to necessitate 
text-books devoted to itself alone, and which it is usual to study rather 
as an introduction to, than as a part of, animal physiology. 
Of the two volumes of which it is intended this book shall consist, 
the articles in the first volume deal mainly with the chemical constitu- 
tion and the chemical processes of the animal body, and with those 
physical and chemical phenomena which are connected with the pro- 
duction and elaboration of the secretions and other fluids of the 
body. The articles in the second volume include the mechanics of the 
circulation and respiration, and of special muscular movements ; the 
general physiology of muscle and nerve ; the special senses ; and the 
functions of the central nervous system. 
It is nearly twenty years since the publication in six volumes of the 
important " Handbuch der Physiologie," under the editorship of Pro- 
fessor L. Hermann. The articles in that book, as in this, were under- 
taken by physiologists who were specially conversant with the particular 
branches of the science with which they severally dealt ; and since most 
of the articles in it are prefaced by short historical introductions, 
and interspersed with abundant references to the literature of the 
subject, the whole work constitutes a storehouse of information, 
which has proved of great value to teachers and investigators. But 
the size of the work, and the fact that it is written in the German 
language, have limited its utility to students in this country ; moreover, 
in the course of the twenty years that have elapsed since its appearance, 
rapid progress has been made in every branch of physiology, so that 
several of the articles in it have been long out of date. Nevertheless 
its publication served both to lay a firm foundation for the exposition of 
the science in its modern aspect, and also to clear the ground for all 
future publications of a similar character. It has thus been a marked 
advantage, in preparing many of the articles for the present book, to have 
had the work of Hermann and his coadjutors to refer to ; and although 
due acknowledgment is made both of this and of other sources of infor- 
mation in the articles themselves, it has seemed right specially to 
mention the " Handbuch " in this preface. 
University College, London, 
February 1898. 
