PREFACE TO FOURTH EDITION. 



The cordial reception with which these Outlines continue 

 to be received shows that the effort to keep them abreast of 

 bacteriological advance is appreciated by students of dairying. 

 An exposition of the principles of bacteriology as applied to 

 dairy problems is now recognized as an essential part of dairy 

 science, for modern dairy practice is rapidly adopting the 

 methods that have been developed through bacteriological 

 study. 



Although a thoroughly satisfactory explanation has not as 

 yet been given for all the phenomena connected with milk 

 and its products, still a better understanding of these prob- 

 lems has been rendered possible through the light that has 

 been thrown upon these questions by scientific study from a 

 bacteriological point of view. 



A brief glossary is appended. embracing those technical terms 

 that are necessarily employed. My acknowledgments are due 

 to the following parties for the loan of cuts: Wisconsin 

 Agricultural Experiment Station: Western Creamery, San 

 Francisco, Cal.; Cornish, Curtis and Greene, Ft. Atkinson, 

 Wis.; and A. H. Reid and Co., Philadelphia, Pa. 



H. L. RUSSELL. 

 Wisconsin Dairy School, 

 Madison, Wis., Dec., 1898. 



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