PREFACE. 



BACTERIOLOGY is just now in transition from 

 the natural history stage to the scientific. The 

 former aspect is adequately treated in some good 

 and comprehensive manuals which attempt 

 to bring together all the available data, and 

 there exist also some good short text-books 

 which contain, in addition to an exposition of 

 methods, the more important facts of the sub- 

 ject set forth with especial view to the needs of 

 the physician. The way in which bacteriology 

 originated and especially the mode of develop- 

 ment of methods of investigation have brought 

 it to pass that the natural history side has been 

 kept in the foreground while the scientific side 

 has been relegated almost exclusively to the 

 sections dealing with protective inoculations. 



This mode of treatment, however, no longer 

 suffices to meet a growing and legitimate de- 

 mand. In this book I wish to present an at- 

 tempt at a critical and comprehensive expo- 

 sition of bacteriology basing it clearly and 

 solidly upon scientific conceptions. I make this 



