FOREWORD. 



No single line of discovery has exerted a more pro- 

 found influence on the scientific thought of the last few 

 decades than has the development of bacteriology. The 

 researches of Pasteur, Koch, and their successors, opened 

 a field of inquiry that has not only revolutionized all of 

 the biological sciences, but also the applied lines of 

 thought. Medicine was the first of these sciences to re- 

 ceive the impetus from such discoveries, but it is no less 

 true that they exert an equally profound effect on agri- 

 cultural sciences. Too long has agriculture been consid- 

 ered simply an art a vocation which one had to learn 

 wholly in the school of experience, but the serious student 

 of farm life finds it necessary to understand the phenom- 

 ena of the plant and animal world and to combat or util- 

 ize successfully the activities of various microscopic or- 

 ganisms. It is therefore essential, even in a practical 

 course, that this important subject be properly consid- 

 ered. The text here presented deals with the subject 

 briefly, but it is designed to give a comprehensive treat- 

 ment of the different relations which the bacteria bear 

 to problems of farm life. At best, it can only serve to 

 stimulate the interest of the student to pursue this sub- 

 ject more in detail as opportunity permits. 



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