PREFACE 



THOUGH nominally a third edition of Bacteria in Relation to the 

 Economy of Nature, Industrial Processes, and ttye Public Health, this 

 is, speaking generally, a new book. Several new chapters have been 

 added, and the whole has been enlarged and revised. 



The book is an attempt to set forth a simple general statement of 

 our present knowledge of bacteria, especially as they are related to the 

 public health. Theoretical and practical text-books of bacteriology 

 abound, but as a rule they deal largely, and rightly so, with laboratory 

 methods and technique. The general student of hygiene and the 

 medical officer of health require, however, an elementary book in 

 which, whilst ample laboratory facts are recorded, the subject is 

 viewed broadly and particularly as it concerns the practical everyday 

 problems of health and preventive medicine. This book is aimed to 

 meet that requirement. 



I am indebted to many friends and colleagues for suggestions and 

 criticisms, and for a number of illustrations. In addition to a number 

 of cliches used in former editions, some of which were kindly lent 

 by the Scientific Press, Limited, from the Atlas of Bacteriology, 

 by Slater & Spitta, I have to express my obligations to the 

 Controller of His Majesty's Stationery Office, the Secretary of the 

 Eoyal Commission on Sewage Disposal, and the Chairman of the 

 Main Drainage Committee of the London County Council, for permis- 

 sion to use several blocks illustrating sewage bacteria derived from 

 cultures obtained by my friend, Dr Houston, in the course of his 

 sewage investigations. I am in a similar way much indebted to Mr 



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