INTRODUCTION XX111 



conditions or in the hands of certain individuals. This limi- 

 tation is a necessity, however, in an elementary course of 

 instruction. Its objection is partially met by references to 

 text-books and other publications where other methods are 

 described. It is very important that the student familiarize 

 himself with at least a few of the more important books and 

 periodicals dealing with bacteriology. They are the source 

 to which he must go later for information on this subject, 

 and consequently a knowledge of their nature and how to use 

 them may be of unmeasured value. 



