PREFACE TO FIRST EDITION 



The considerations which led the writer to add this 

 laboratory guide of bacteriology to the number of such 

 guides already in existence were of various nature and 

 may be briefly set forth here. 



Probably no branch of biological science has ad- 

 vanced so rapidly during the past few years as the 

 science of bacteriology, and it is difficult even for an 

 active laboratory worker to keep abreast of this ad- 

 vance. A textbook or guide fixes the status of the 

 science at the time of its writing, but almost before it 

 leaves the press it becomes antiquated. Revisions, 

 corrections, and additions are necessary at short 

 intervals in order to keep a pubUcation of this kind 

 approximately up to date. There is, therefore, almost 

 at any given moment room for a new publication to fill 

 the want of a progressive instructor for a guide that 

 gives the latest accepted rules and practices of the 

 laboratory. The value of such a publication will 

 fee enhanced by a plan and arrangement of sufficient 

 flexibility and latitude to allow the instructor and the 

 student to enter such additions and corrections as serve 

 to bridge over the time between editions. 



Medical students entering on a course in bacteri- 

 ology often have had too little previous laboratory 

 training in methods of precision. It is a matter of 

 importance for the instructor to put himself in the atti- 

 tude of mind of the student and to try to appreciate 

 his difficiflties in understanding details. Many of 



