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PREFACE TO THE THIRD EDITION 



WHILE no notable discovery has been recorded in bac- 

 teriology since the appearance of the second edition of this 

 book, much extension and consolidation of previous know- 

 ledge have been effected. This has necessitated revision 

 and enlargement of nearly all parts of the book. 



A war on highly-cultivated soil, with troops occupying 

 the same ground for lengthy periods, has very forcibly 

 obtruded the pathogenic abilities of many faecal bacteria. 

 Tetanus, typhoid, paratyphoid, and dysentery bacilli, the 

 bacillus of malignant oedema, and the faecal pyogenic 

 streptococci, have all been in evidence. Bacillus WdcMi, 

 under one or other of its many names, has also claimed 

 much attention in connection with gaseous gangrene. 

 In the case of these organisms, however, new developments 

 have been chiefly in the directions of pathology and treat- 

 ment rather than in bacteriology. 



We have considerably extended our article on and 

 devoted an appendix to the meningococcus an organism 

 whose life outside the human body remains largely a 

 matter for conjecture. We have collected in one chapter 

 a summary of the little that is known about the filterable 

 viruses, and have also dealt with anaphylaxis and the 

 preparation of vaccines. In accordance with the advice 

 of Professor David Ellis, we have substituted the classifi- 

 cation of Migula for that of Hueppe. 



Few bacteriological investigations are free from possible 

 fallacy or insusceptible of wrong deduction. The influ- 

 ence of anti-typhoid inoculation on the Widal test, the 

 absence of tubercle bacilli in milk from tuberculous udders, 

 the absence of colon bacilli from polluted water, the 

 incorrect selection of organisms in the preparation of bac- 

 terial vaccines, and the fact that the popular Wassermann 



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