PREFACE TO THE FIRST EDITION ix 



philosophy, botany, or zoology, an outlook over the problems, facts, 

 theories, and hypotheses of life ; in other words, I wished to give 

 him an introduction to general physiology, and thus afford him an 

 idea of the important theoretical basis of his study. It is not easy 

 to adapt oneself to these diverse aims. How far I have succeeded 

 in doing this, only the judgment of the reader can decide. I 

 bespeak his indulgent criticism. 



I gratefully acknowledge my obligations to all my friends who 

 have taken active part in the planning, developing, and com- 

 pleting of my task, and especially to Mr. Gustav Fischer, who has 

 shown great liberality in the publication of the book. 



THE AUTHOR. 



London, November 4, 1894. 



