PREFACE 



THIS book is intended to serve as an introduction to Bacteriology 

 in all its branches, though more attention has been bestowed on 

 that aspect of the subject which is of most interest to students of 

 technical and agricultural bacteriology. 



Of late years, great strides have been made in this fascinating 

 subject, and an attempt has been made to incorporate in the text 

 the recent developments that are of fundamental importance. In 

 some instances, as for example in our conceptions of the anaerobic 

 bacteria, important changes have taken place. In other instances, 

 however, our knowledge is still incomplete and rudimentary. 

 Controversial questions, and matters requiring a technical know- 

 ledge of a special nature have been either omitted or have received 

 only a passing reference. In all cases, where a technical application 

 of bacteriology is discussed, the aim has been the demonstration of 

 the fundamental principles which underlie that application, rather 

 than the discussion of the details. 



It has been deemed advisable to introduce a comparatively large 

 amount of matter of purely theoretical interest, because in no other 

 branch of science is a theoretical knowledge more necessary than 

 in the science of Bacteriology. When one bears in mind that the 

 organisms which are here discussed are visible only with the highest 

 magnifications of the microscope, are very changeable in their nature, 

 and are everywhere present around us, the need for a thorough 

 theoretical training becomes obvious, even for those who wish only 

 to make practical applications. 



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