PREFACE. 



THE want of a text-book in the English language to which students 

 could turn for information beyond that contained in the ordinary 

 manuals has long been felt by teachers of physiology in this country. 

 The most extensive of the existing text-books do not aim at giving 

 the full and precise information nor the references to original 

 authorities which are required by the advanced student. It has 

 hitherto been necessary for those who seek such information to consult 

 original articles an operation which frequently involves a familiar 

 acquaintance with foreign languages and an expenditure of time rarely 

 at the disposal of the student. The present work is not intended 

 altogether to supersede this consultation of original papers, but will, 

 it is hoped, reduce the need of it to more reasonable limits, and will, 

 moreover, by the references to literature which throughout form an 

 important feature of each article, facilitate such study where it is still 

 necessary. 



A book of this character, from the enormous amount of literary 

 labour which is involved in its production, and from the progressive 

 character of the science with which it deals, could hardly be undertaken 

 by one person. The editor has been fortunate enough to secure the 

 co-operation of many of the leading physiologists in this country, each 

 of whom deals with some branch of the subject to which he has given 

 special attention. Accordingly the reader will find in each article, in 

 addition to information as to the present state of knowledge as com- 

 plete as it has been possible to make it, many original observations 

 upon the matter to which it relates. 



The subjects of generation and reproduction have been omitted in 

 this text-book, because, although strictly speaking appertaining to 

 physiology, they are studied almost entirely by morphological methods, 

 and are more conveniently treated in connection with morphology. It 

 has therefore been decided that it would be better not to swell the bulk 

 of these volumes, which have already grown beyond the limits originally 

 intended, by the introduction of subjects such as these, which possess 

 an enormous recent literature, and are exhaustively dealt with in 

 special works accessible to every student. The same remark will apply 

 to the general physiology of the cell, a branch of biology which has 



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