INTRODUCTION xiii 



within a limited space the result of the innumerable labours 

 which have accumulated on microbes and their poisons and 

 which have been pursued in the most varied directions, 

 M. Burnet has succeeded in accomplishing the task in a 

 remarkable fashion. I am sure that those who read will share 

 my opinion, and I wish this book the most widespread 

 popularity. 



ELIE METCHNIKOFF. 

 Paris, 191 i. 



