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PREFACE. 



IN the following pages the attempt has been made 

 to group together those facts in Bacteriology which 

 will constitute a sufficient text-book for the student and 

 which are of direct practical value to the physician 

 and health officer. Laboratory technique is given in 

 its essentials and to such an extent as is necessary to 

 make bacteriological methods plain to the physician, 

 to guide him in making the simple examinations pos- 

 sible in his office, and to show him under what 

 conditions he can obtain diagnostic or other help from 

 bacteriological examinations in laboratories. The phy- 

 sician can readily understand and apply the essentials 

 of bacteriology, but the actual carrying out of the 

 more difficult examinations should be left to the 

 trained bacteriologist. 



Such subjects as the chemical changes produced by 

 bacteria, infection, immunity, the nature and use of 

 protective serums, and the diagnostic value of bacte- 

 riological cultures, are particularly emphasized, since 

 knowledge of such subjects is of special importance to 



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