PREFACE TO THE SECOND EDITION 



In the preparation of this second edition the text has been re- 

 vised throughout, but the changes have been in the nature of 

 minor corrections and the addition of new matter to bring the text 

 up to date. The general plan of the book has been preserved, 

 keeping in mind its purpose as an introduction to the study of 

 pathogenic micro-organisms. 



Subjects in controversy, such as the pathogenic r61e of Bacillus 

 influenza or of Bacillus typhi-exanthematici, have received only 

 brief mention, but some references to the literature have been 

 given for the possible use of more advanced students. On the 

 other hand more conclusive advances in microbiology, such as the 

 recent studies on botulism, yellow fever, rat-bite fever and trench 

 fever have been included in the text. Several new illustrations 

 have been added, the credit for which is indicated in each instance. 

 The index and the table of contents have been made quite full 

 in order to render the text readily accessible and to present to the 

 student a skeleton outline for the review of each chapter. 



My thanks are again due to Mrs. MacNeal for assistance, 

 especially in the preparation of the index. 



W. J. MacNeal 

 New York 



