INTRODUCTION TO THE FIRST EDITION 



By a process of adaptation and growth, the branch of science com- 

 monly recognized as "Bacteriology" has for many years included, 

 besides the bacterial forms, those microorganisms yielding to the same 

 laboratory methods of study and investigation. This is a policy or 

 purpose instituted by Pasteur. It is also the result of investigations 

 and added knowledge, more definite arrangements of available facts, 

 and the highly specialized training required for the work. In short, 

 technic together with the economic relations of the subject-matter 

 has no little influence in placing limitations. In the light of such cir- 

 cumstances, it appears more pertinent to designate this text-book 

 as "Microbiology," perhaps not the best term, but one much in accord 

 with French usage. 



Agriculture, Domestic Science and certain other courses in scientific 

 schools and colleges call for the treatment of the subject in such a man- 

 ner as to make it basic to the interpretation of such subjects as air 

 impurities, water supplies, sewage disposal, soils, dairying, fermenta- 

 tion industries, food preservation and decomposition, manufacture 

 of biological products, transmission of disease, susceptibility and im- 

 munity, sanitation, and control of infectious or contagious diseases. 

 A strong effort has been made to provide the fundamental and guiding 

 principles of the subject and to show just how these principles fit into 

 the subjects of a more or less strictly professional or practical nature. 

 Here the instructional work of the microbiologist stops in most educa- 

 tional institutions and the instruction of the practical or professional 

 man begins. 



Because of the extreme massiveness and diversity of the subjects, 

 Agriculture and Domestic Science and Industrial Vocations in general, 

 a comprehensive consideration of the subject is demanded. Elimina- 

 tion of many features not only becomes difficult but really precarious, 

 because so many avenues are open to the student that pertinency cannot 

 always be foreseen or determined. It is well to remember, too, that 



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