PREFACE. THIS book is intended to serve as an introduction to Bacteriology in all its branches, though more attention has been bestowed on that aspect of the subject which is of most interest to students of technical and agricultural bacteriology. Of late years, great strides have been made in this fascinating subject, arid an attempt has been made to incorporate in the text the recent developments that are of fundamental importance. In some instances, as for example in our conceptions of the anaerobic bacteria, important changes have taken place. In other instances, however, our knowledge is still incomplete and rudimentary. Controversial questions, and matters requiring a technical knowledge of a special nature have been either omitted or have received only a passing reference. In all cases, where a technical application of bacteriology is discussed, the aim has been the demonstration of the fundamental principles which underlie that application, rather than the discussion of the details. It has been deemed advisable to introduce a comparatively large amount of matter of purely theoretical interest, because in no other branch of science is a theoretical knowledge more necessary than in the science of Bacteriology. When one bears in mind that the organisms which are here discussed are visible only with the highest magnifications of the microscope, are very changeable in their nature, and are everywhere present around us, the need for a thorough theoretical training becomes obvious, even for those who wish only to make practical applications. In addition to the published researches which have been consulted, I desire to ackriowledge the help which I have obtained from the following books Lafars Handbuch der tech, nischen Jfykologie, Newmans Bacteriology and the Public Healih, Greens Fermentation, and Muir and RitchieJs Manual of Bacteriology. Further, I wish to acknowledge my indebtedness to the Rev. Robert Barr, M. A., to Prof. I,. A. L. Icing, M. A., and to other friends for their valuable assistance during the compilation of this rvork. n A v I n ELLIS. CONTENTS CHAPTER I. SECTIOX PAGE 1. INTRODUCTI - O N - 1 4. D0 BACTERIA BE LONG TO THE VEGETABL O E R TO THE ANIMAL KISGDOX - - - - - - - 12 CI-IAPTER 11. 1. THE CILIA OF BACTERIA - - - - - - - 1 General nature-development of cilia-nature of motility. 2... --This text refers to an alternate Paperback edition.