PREFACE TO SIXTH EDITION. 



The three years that have elapsed since the appear- 

 ance of the Fifth Edition of this book have been particu- 

 larly fruitful in works of bacteriological interest. Light 

 has been shed upon the etiology of several important 

 diseases of man, notably epidemic cerebro-spinal men- 

 ingitis and dysentery. Interest has been re-awakened 

 in the subject of tuberculosis ; we have been made 

 familiar with a group of micro-organisms in certain 

 ways allied to bacillus tuberculosis, and having the 

 property of causing conditions more or less suggestive 

 of tuberculosis ; and much of fundamental importance 

 has been contributed to our understanding of the mech- 

 anism of infection and immunity. Wherever appro- 

 priate to a book of this character these advances have 

 been included. 



The chapter on suppurative and inflammatory condi- 

 tions has been enlarged with a description of the causa- 

 tive agent of epidemic cerebro-spinal meningitis ; that 

 on tuberculosis with a summary of our knowledge of the 

 acid resisting bacilli that are in many ways allied to 

 bacillus tuberculosis, and with a description of the more 

 important pathogenic streptothrices ; to the chapter re- 

 lating to the infections of the intestinal canal a sum- 

 mary of the new work on dysentery with a description 

 of the micro-organism now believed to be the cause of 

 that disease has been added; and the comments upon 



