PREFACE TO THE SECOND EDITION. 



The cordial reception with which this book has met, 

 and the demand for a second edition, afford the author 

 no small degree of gratification. In revising The Prin- 

 ciples of Bacteriology advantage has been taken of the 

 valuable suggrestions kindlv offered bv the reviewers of 

 the first edition, for which the writer here acknowledges 

 his indebtedness. 



The section of the work devoted to descriptive bac- 

 teriology has been somewhat extended, but no effort 

 has been made to cover the entire field, only those spe- 

 cies being introduced that are comparatively common 

 or of importance in enabling the student to acquire a 

 fundamental working knowledge capable of wider ap- 

 plication. W'^herever practicable, these descriptions have 

 been supplemented by illustrations, for the majority of 

 which the author is responsible. The introduction of 

 colored figures in the text is a new feature in this edi- 

 tion, and one which should increase its usefulness. A 

 sketch of the evolution of our knowledge upon immu- 

 nity and infection has been introduced, and an outline 

 of apparatus necessary for a beginner's laboratory has 

 been appended. 



