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PREFACE 



PRELIMINARY to studies on the bacterial flora of cultivated 

 soils, the writer undertook an arrangement of the several hun- 

 dred species of bacteria already described, with the view of 

 identifying the forms isolated, or at least of determining whether 

 they were new to science. The labor involved in this arrange- 

 ment has been so great that it was decided to embody the 

 results in the present form that others might have the advan- 

 tage of them. The writer does not claim that the system of 

 arrangement is perfect or not open to criticism. The best use 

 only could be made of the facts and material available. The 

 present tables serve, therefore, only for purposes of identifica- 

 tion, and not necessarily for those of classification. 



For this reason the present book has been termed a 'Manual 

 of Determinative, rather than one of Systematic, Bacteriology. 



To the student working in the laboratory the determination 

 of unknown bacteria has been almost impossible, except with 

 the expenditure of an amount of labor which was impracticable. 

 With the use of the present manual it is believed that the 

 teacher can place a given culture in the hands of his pupil and 

 expect him to determine it, as is done with other organic forms. 

 It is therefore hoped that the present work will serve a useful 

 purpose as a laboratory manual. 



The chapter on morphology has been appended in order to 

 make clearer the system of classification into orders and 

 genera. 



