vin PREFACE TO THE FIFTH EDITION 



variety of infection and to incorporate in the more important chapters, 

 brief discussions of the principles underlying sanitary procedure. 



In the sections on technique we have eliminated many methods 

 which we have ceased to use ourselves. At the laboratory of the 

 Bacteriological Department of the Medical School of Columbia Uni- 

 versity we have had the opportunity of having advanced students 

 and staff try out a great many bacteriological procedures and have, 

 in consequence, been able to eliminate a number of methods that, as 

 matters of routine, have been practically dropped from our practice. 

 We have considerably simplified the section on media. The newer 

 methods of titration have been added. 



The immunological section has been considerably changed and we 

 think simplified. It is not the purpose of a book of this kind to pre- 

 sent a critical thesis on theoretical immunity. We have, therefore, re- 

 stricted ourselves to the exposition of the more important principles 

 and practical methods needed by routine laboratory workers. Short 

 sections on the normal bacterial flora of the human body have been, 

 added, with particular consideration of the important work done in 

 recent years by Herter, Kendall, Rettger and others. Most of the 

 sections dealing with the pathogenic microorganisms themselves have 

 been completely rewritten and the order of presentation consid- 

 erably altered in order to bring together, more logically, infections 

 which are usually considered together from the clinical point of 

 view. The diagnostic and therapeutic principles in which bacteri- 

 ological and immunological reasoning and technique are involved have 

 been thoroughly dealt with. 



The section on Protozoa has been completely revised by one of us 

 along the same general lines adopted for the revision of the bacteri- 

 ological section. 



The writers realize that the inclusion of clinical and epidemio- 

 logical data in a Textbook of Bacteriology is considerably at variance 

 with the usual treatment given to the subject in books of this kind. 

 But it is hoped that this manner of treatment will add considerably to 

 the value of the book for those who are interested in microorganisms 

 particularly in their relationship to clinical and preventive medicine. 



In conclusion great ful acknowledgment is made to a number of 

 our associates in the Department of Bacteriology at Columbia for 

 valuable aid in the preparation of this Edition. Dr. J. 0. Hopkins, 

 Associate in the Department who lias boon working with the patho- 

 genic molds, has rewritten the section dealing with these organisms. 



