4 PREFACE. 



in practice in connection with cases of actual disease. 

 Accidents may occur, it is true, but they are extremely rare 

 as compared with the numerous instances of infection 

 incurred in post-mortems or in surgical operations. 



Bacteriology, as an educational measure of the first 

 importance, belongs in the first, or at the latest, in the 

 second year of a medical course. The student is thus 

 enabled to make use of his knowledge in connection with 

 his clinical studies. The spirit of scientific investigation, 

 and not mere book reading, must be fostered in the student 

 from the outstart, since it is this that leads to progress in 

 medicine and serves to distinguish the true physician from 

 those bound down through blind faith, commercialism or 

 ignorance. 



This edition is thoroughly revised and greatly enlarged. 

 It should be noted that it is a text-book of laboratory work 

 for students. The arrangement of the subject matter is 

 different from that usually met with in text-books, for the 

 reason that it conforms as much as possible to the actual 

 work as carried on, day by day, in the Hygienic Laboratory 

 of the University of Michigan. During the past ten years 

 three laboratory courses in bacteriology have been given 

 annually. Each course covers a period of twelve weeks of 

 daily work, to which the entire afternoon is devoted. Inas- 

 much as this laboratory work is required of all medical 

 students, the number of students which annually take the 

 course at times exceeds two hundred. 



Since it is a beginner's guide and not a manual, it 

 obviously is undesirable to introduce the numerous modifi- 



