PREFACE TO THE SIXTH EDITION. 



THE kind reception and increasing popularity of the 

 PATHOGENIC BACTERIA, by which five editions have been 

 exhausted in thirteen years, are sources of gratification and 

 self-congratulation to the author and the publishers, who 

 have spared no pains to make the work as useful as possible. 



It seems like a supererogation to explain the scope and 

 purpose of a book that already has nearly ten thousand 

 readers, yet there seem to have been some misunderstandings 

 in regard to them. The title explains the scope of the work 

 it is upon the "Pathogenic Bacteria." Those who desire 

 to be informed upon the Non-pathogenic Bacteria or upon 

 the Pathogenic Protozoa must look for information in the 

 numerous works devoted to those subjects, which are now, 

 as the author, when writing this book foresaw they soon 

 would become, entirely too voluminous to be satisfactorily 

 treated in an Appendix or in one or two supplementary 

 chapters. 



The "Pathogenic Bacteria" is a text-book, not an encyclo- 

 pedia. It contains a rather extensive bibliography, but not 

 a complete one. Through it the student is referred to the 

 original writings upon the subjects treated ; to writings that 

 have become classic, that serve as models, that embrace 

 complete bibliographies of the subjects treated, or that are 

 useful because of ingenious experiments recorded, and to 

 writings in which the recent advances of the subject are 

 contained. 



The references are naturally of most use to the advanced 

 student, and the method of referring to the papers by foot- 

 notes has been adopted for the purpose of keeping them in 

 sight without interrupting the continuity of the text for 

 those who do not desire to use them. 



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