PREFACE. IN the following pages the attempt has been made to group together those facts in Bacteriology which will constitute a sufficient text-book for the student and which are of direct practical value to the physician and health officer. Laboratory technique is given in its essentials and to such an extent as is necessary to make bacteriological methods plain to the physician, to guide him in making the simple examinations pos- sible in his office, and to show him under what conditions he can obtain diagnostic or other help from bacteriological examinations in laboratories. The phy- sician can readily understand and apply the essentials of bacteriology, but the actual carrying out of the more difficult examinations should be left to the trained bacteriologist. Such subjects as the chemical changes produced by bacteria, infection, immunity, protective serums, and the diagnostic the nature and use of value of bacte- riological cultures, are particularly emphasized, since knowledge of such subjects is of special importance to 91547 iv PREFACE. the practising physician, in that it enables him- to ob- tain an intelligent grasp of the nature of the infectious diseases. The methods used in the laboratory for the isolation and identification of the typhoid, tubercle, and diph- theria bacilli have been given with especial fulness, as bacteriological examinations of the discharges of per- sons suspected to have typhoid fever, tuberculosis, or diphtheria are now generally made for these bacteria in the laboratories of the health departments of even the smaller cities, because of the manifest importance to the public of knowing where such sources of infec- tion exist. In preparing this book the best works have been freely consulted. Of these, those of Fliigge and Sternberg, on General Bacteriology, and those of Abbott and Mallory and Wright, on Technique, should perhaps be especially mentioned. My sincere thanks are due to Dr. Hermann M. Biggs, the Director of the Bacteriological Laboratory, and tomy colleagues in it, who have so freely furnished me with the results of their original investigations. I wish also to especially acknowledge my indebtedness to Dr. A. R. Guerard, who has given me invaluable aid in the preparation of the book. The illustrations, with the exception of those on malaria and cholera, for which I am indebted to Drs. Welch and Dunham, are almost entirely from photographs taken from cover-glass preparations and cultures by Dr. Edward R. Learning, Instructor in Photography in the Medical Department of Columbia University. NEW YORK, November, CONTENTS. INTRODUCTION. PAGE Historical Sketch of the Development of Bacteriology . . 17 CHAPTER I. The General Characteristics of Bacteria Their Morphology and Structure Vegetative and Spore Forms ... 33 CHAPTER II. The Chemical Composition of Bacteria The Conditions Suitable for their Growth ....... 50 CHAPTER III. Vital Phenomena of Bacteria Motion, Heat, and Light ProductionChemical Effects Ferments, Ptomains, Toxins . 58 CHAPTER IV. The Relation of Bacteria to Disease ..... 85 CHAPTER V. Immunity . . . . . . . . . . 102 CHAPTER VI. Theories of Infection, Immunity, and Recovery . . . 118 Infection CHAPTER VII. 128 viii CONTENTS. CHAPTEK VIII... --This text refers to the Paperback edition.