PREFACE. 



This little book was designed by the writer to serve the needs 

 of the medical student preparing for examination, and for the 

 practitioner of medicine who desires to acquaint himself with the 

 principal facts of the rapidly growing science of bacteriology. An 

 effort has been made to reduce the subject matter to as concrete 

 a form as possible. 



While the literature of the subject of immunity is as vast almost 

 as the rest of bacteriology, yet it is hoped that the chapter in this 

 book on immunity gives in outline the essential accepted teachings 

 on the subject. 



Minute details of cultures and technic are not given. They must 

 be sought for in books on descriptive bacteriology. 



The author has drawn very freely from many standard text- 

 books. Many illustrations are from Kalle & Wasser-mann's 

 Atlas, Williams, McFarland, Tyson's Practice and Abbott. 



The writer's best thanks are tendered to Dr. Herbert Fox of the 

 University of Pennsylvania (Pepper Laboratory) to whom entire 

 credit is due for the chapters on filterable viruses; the rearrange- 

 ment of chapter, and the new matter that has been added 

 throughout the book. 



To the firm of P. Blakiston's Son & Co. the writer is indebted 

 for valuable aid. 



ROBERT. L. PITFIELD. 



