Vlll INTRODUCTION. 



in their educational history where practice and the science upon which 

 practice should be founded are amalgamated. The practical man in 

 Agriculture, and Applied Sciences generally, too frequently is so extremely 

 traditional in his practice that he utterly fails to separate the true from 

 the false, or, in other words, does not exercise his discriminative powers 

 at all, but depends entirely upon so-called haphazard methods and self- 

 willed processes. This factor operates against the proper development 

 and logical study of any branch of science in its relation to the farmer, 

 or manufacturer. 



The plan of a text-book in Microbiology which seeks to furnish basic 

 principles, to train the mind in logical development and adjustment, 

 and to prepare the student to undertake an intelligent study of strictly 

 professional or practical subjects, must assume a definite and systematic 

 arrangement. With this in mind, the text has been divided into three 

 distinct parts: Morphological and Cultural, or that which deals with forms 

 and methods of handling; Physiological, or that which deals strictly with 

 functions, the key to the applied; Applied, or that which reaches into the 

 application of the facts developed to the problems met in the study of 

 professional or practical affairs. 



In a text-book, the product of several hands, there is the most serious 

 difficulty in obtaining unity of thought and expression without repetition; 

 besides, that very conspicuous weakness of emphasizing some features 

 unduly while other features of importance are scarcely mentioned, con- 

 fronts us. A most earnest attempt has been made to overcome these 

 faults as far as possible, but a complete mastery of them cannot be ex- 

 pected in the first product. However, what is lacked in unity and con- 

 tinuity of expression and in balance, we sincerely hope will be made up, 

 in part at least, by the selection and the value of the material contributed. 



Laboratory features of microbiology have been eliminated wher- 

 ever it has been practicable. Should any demonstrations be added 

 or needed, we have felt that they may be easily supplied by the instructor, 

 who, of course, will be governed by local facilities and conditions. Al- 

 though no space has been given to laboratory exercises, it should not be 

 gathered that the authors of this book are any the less earnest in urging 

 a well-organized laboratory course to supplement the general instruction 

 as an essential factor to a working appreciation of the subject. 



In matters of spelling, new words, and phrases, conservatism has 

 controlled. Arbitrary decisions and selections have been forced in 



