xii INTRODUCTION 



In the almost untilled field of industrial bacteri- 

 ology there is need for a fuller appreciation of the 

 value of bacteriological methods and principles. Many 

 great industries are based wholly upon the proper 

 selection and adaptation of micro-organisms, and a 

 timely and discriminating utilization of their products. 

 Loose and empirical methods have been in force in the 

 past, but these must eventually give way to a more 

 precise and truly bacteriological technic. 



Agricultural bacteriology is just now much in the 

 public eye, and it would be gratuitous to prophesy 

 the results that may reasonably be anticipated in this 

 direction. Here again crude, rule-of-thumb, "prac- 

 tical " ways of doing things are being supplanted by the 

 scientific, the reasoning, and the precise. 



To the student, whether in medical, hygienic, or 

 industrial bacteriology, proper technical methods of 

 work must always have a peculiar value, since without 

 their aid advance is impossible, and stumbling and 

 disastrous missteps are certain. A comprehensive out- 

 line of modern bacteriological methods, therefore, is a 

 necessary adjunct to obtaining a true and full under- 

 standing of the underlying principles and tendencies 

 of the science. The technic of bacteriology is one 

 of its greatest contributions to both science and art, 

 and the use of so valuable and simple a tool should be 

 mastered not only by the biological teacher and in- 

 vestigator, but by practical workers in medicine, 

 hygiene, and many other fields. 



EDWIN O. JORDAN 



