PREFACE. 



This volume is the outgrowth of an attempt to revise the well- 

 known William's Manual of Bacteriology, undertaken at the invi- 

 tation of the Publishers, Messrs. P. Blakiston's Son and Co., very 

 cordially seconded by Dr. Williams, who kindly placed the mate- 

 rial of the previous editions at my disposal. The text has been 

 very largely rewritten and the order of treatment considerably 

 altered. Many of the illustrations of Dr. Williams have been 

 retained and, as they have not been acknowledged in the legends, I 

 wish to express my special obligation for them in this place. 



The book is intended as an introduction to the study of patho- 

 genic micro-organisms and is designed especially for the use of 

 physicians and students of medicine. During the past decade, 

 the parasitic protozoa have assumed an importance which places 

 them almost on a par with the bacteria as pathogenic agents, and 

 the extension of bacteriological methods to the study of molds, 

 yeasts, filterable viruses and protozoa has tended again to re- 

 unite the various portions of this field of knowledge, much as it 

 was in the days of Pasteur. The attempt has here been made to 

 outline the subject and to present a few examples under each 

 important heading, in the hope that the student may become 

 acquainted with the broad principles of the science and appreciate 

 the variety of procedures, conceptions and organisms with which 

 it deals. Part I is devoted to a description of technical procedures, 

 Part II to the general biology of micro-organisms and Part III 

 to a consideration of individual microbes. Much has of necessity 

 been omitted and many topics treated only very briefly. 



In the preparation of the manuscript considerable use has 

 been made of the text-books of McFarland, Jordan, Marshall, 

 and of Hiss and Zinsser, and the Handbuch der pathogenen Mikro- 

 organismen of Kolle and Wassermann and Doflein's Lehrbuch der 



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