PREFACE TO THE FOURTH EDITION. 



An experience of nearly thirty years in the teaching of 

 Bacteriology has convinced the author that students of this 

 subject need a comprehensive grasp of the entire field and 

 special training in fundamental technic before specializing 

 in any particular line of work. Courses at the University 

 are arranged on this basis. One quarter is devoted to General 

 Bacteriology. During the second and third quarters the 

 student has a choice of special work in Pathogenic, Dairy, 

 Soil, Water, or Chemical Bacteriology. A second year may 

 be devoted to advanced work in any of the above lines, to 

 Immunity and Serum Therapy or to Pathogenic Protozoa. 



This text-book is intended to cover the first or introductory 

 quarter's work, and requires two classroom periods per 

 week. Each student is compelled to take three laboratory 

 periods of three hours each per week along with the class 

 work. The outline of the laboratory work is given at the 

 end of the text. Results attained seem to justify this plan. 

 A text-book is but one of many pedagogical mechanisms and 

 is not intended to be an encyclopedia of the subject. 



During the preparation of this work the author has made a 

 thorough review of the literature of Bacteriology, covering 

 the standard text-books as well as works of reference and 

 the leading periodicals dealing with the subject. Thus the 

 latest information has been incorporated. 



No attempt has been made to give detailed references in a 

 work of this character. 



The photomicrographs are original except where otherwise 

 indicated and are all of a magnification of one thousand diam- 

 eters where no statement to the contrary appears. These 

 photographs were made w^ith a Bausch & Lomb Projection 

 Microscope fitted with a home-made camera box. Direct 



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