PREFACE. 



Many of the speculations propounded in this work, as well 

 as its entire plan, are original. It may consequently be of 

 service to the reader to have it prefaced by a brief account 

 of its purpose and of its leading ideas, written from the 

 Author's point of view. 



My chief purpose has been to state and to discuss what I 

 regard as the special and characteristic principles of life. In 

 the two chapters on the Chemistry and the Dynamics of Life, 

 I have treated of the relation of life to ordinary matter and 

 force : a relation which is now tolerably well understood. But 

 the most important part of this work treats of those vital 

 principles which belong to the inner domain of life itself, as 

 distinguished from the principles which belong to the border- 

 land where life comes into contact with inorganic matter 

 and force. To that border-land belong such laws as those of 

 nutrition and respiration : while to the inner domain of life 

 belong the laws of organization and of mind. 



In this inner domain of life, on which dynamics and 

 chemistry have scarcely any light to throw, we find two 

 principles which are, as I believe, co-extensive with life and 

 peculiar to it : these are Habit and Intelligence. 



I am compelled to use the word Habit in an unusually wide 

 sense, though, as I think, a perfectly accurate one. I mean 

 by habit, that law in virtiie of which all the actions and 

 the characters of living beings tend to repeat and to T)err)etuatf 



