PREFACE TO THE EIGHTH EDITION 



THE time that has elapsed since the last edition of 

 this book has witnessed many important advances in our 

 knowledge of bacteriology and its manifold applications. 

 In the main, however, these have not materially af- 

 fected the basic principles so essential to the education 

 of the beginner. 



Such new methods of work as have been found to be 

 of real value have been incorporated. 



The article on infection and immunity has been prac- 

 tically re-written and stress has been laid upon the 

 newer views of phagocytosis. 



Recent work on protective vaccination and the 

 preparation of antisera has been reviewed. 



A great deal that appeared in former editions has 

 been eliminated in recognition of the rapid development 

 of the science. 



It is believed these changes will serve to maintain 

 the reputation the book has won as a safe guide for the 

 beginner. A. C. A. 



Laboratory of Hygiene, University of Pennsylvania, 1909. 



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