PREFACE TO THE SIXTH EDITION 



THIS edition has been thoroughly revised and new chapters 

 on Protozoa and Opsonic Technic added. While this work is 

 intended as an introduction only, I have endeavored to make 

 it complete enough to permit the student and the practitioner 

 by its aid to examine and identify any or all of the important 

 bacteria. It aims to contain the essentials of larger works and 

 at the same time serve as a guide in the laboratory of the 

 student, the clinician, and the sanatarian. 



Medical bacteriology has gradually broadened its scope, so 

 that now the accomplished bacteriologist must be well versed 

 not only in a knowledge of allied microorganisms, but also in 

 the knowledge of the higher life forms, the normal and path- 

 ologic anatomy of birds, mosquitoes, flies, rats, and fleas, 

 through whom important diseases are transmitted to man. 

 Although from the beginning bacteriology has been closely 

 associated with zoology, never before -has the subject required 

 such an extensive knowledge of ..all biologic sciences, to say 

 nothing of the depths in chemistry the studies of immunity 

 have gradually entered. Elementary microbiology should be 

 taught in close association with other sciences and, therefore, 

 in a university as a preparatory course, while an advanced 

 course only should be taught in medical schools in connection 

 with pathology. 



M. V. BALL. 



WARREN, PA., October, 1908. 



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