PREFACE. 



MY object in writing this book is simply to indicate 

 that there is a natural history of disease, as well as of 

 plants and animals. I have not attempted to deal with 

 the subject at great length, far less exhaustively, but 

 merely to illustrate general principles by a few carefully 

 selected examples. 



The subject is a novel one, and doubtless a more 

 extended study will serve to show that many of my 

 conclusions are fallacious. I trust that such errors may 

 be speedily rectified by any person who has opportu- 

 nities of testing my opinions practically. It must be 

 borne in mind that it is a much easier task to write 

 concerning the habits of animals than to describe their 

 diseases ; nevertheless, the facts at our disposal clearly 

 indicate that disease is controlled by the same laws 

 which regulate biological processes in general. 



J. B. S. 



