INTRODUCTION. 



By a process of adaptation and growth, the branch of science commonly 

 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 eco- 

 nomic relations of the subject-matter has no little influence in placing 

 limitations. In the light of such circumstances, 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 and Domestic Science call for the treatment of the sub- 

 ject in such a manner as to make it basic to the interpretation of such 

 subjects as air impurities, water supplies, sewage disposal, soils, dairy- 

 ing, fermentation industries, food preservation and decomposition, 

 manufacture of biological products, transmission of disease, susceptibility 

 and immunity, 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 educational 

 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, a comprehensive consideration of 

 the subject is demanded. Elimination 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 Agriculture and Domestic Science, unlike 

 such aggregate subjects as Engineering and Medicine, because of their 

 youth, have not developed to that stage in their educational history where 



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