PREFACE TO THE THIRD EDITION 



Apart from the war, this edition has been prepared under the shadow of a double 

 misfortune. Early in 194:1, Professor Topley accepted the post of Secretary of 

 the Agricultural Research Council, and thereby took a step that rendered his 

 further participation in this book impossible. To replace him, I was fortunate 

 in enlisting the co-operation of our former colleague. Professor Miles. Together 

 we began the arduous task of revision. Our work, however, had not progressed 

 far before the second blow fell. Quite suddenly in January, 1944, Topley died. 

 The effect of this second misfortune was almost as serious as the first. Although 

 Topley could have made no direct contribution to the text, his criticism and advice 

 would have been constantly available, and he would have helped us to maintain 

 that uniformity of presentation for which he and I had always striven. On Miles, 

 in particular, the burden weighed heavily, since, in taking over those parts of the 

 book for which Topley had previously been responsible, he was deprived of counsel 

 that would doubtless have proved invaluable to him. 



There is no call to write a long preface. We have endeavoured not merely to 

 bring the book up to date, but to present the new additions to our knowledge 

 in a manner worthy of their importance. One chapter — that on Soil Microbiology 

 — has been deleted, but two new chapters, on Chemotherapy and on the Bacteriology 

 of Air, have been added. For the sake of convenience we have divided the previous 

 Bacterium chapter into three, giving separate recognition to the genera Shigella 

 and Salmonella. We have also removed the psittacosis-lymphogranuloma group 

 of diseases from the other filtrable virus diseases with which they were associated 

 and awarded them a chapter of their own. Except for these alterations, the form 

 of the book remains unchanged. In the first two editions we tried to ensure that 

 scientific literature from all parts of the world was fairly represented, but in the 

 present edition we have suffered under a handicap imposed by the war, which has 

 seriously curtailed the inflow of journals from many parts of Europe as well as, 

 of course, from Japan. This gap we shall look forward to filling in the future. 

 Partly because of the necessarily one-sided picture we have been obliged to paint, 

 we have thought it wise to present our evidence in greater detail than might other- 

 wise have been necessary, and to be perhaps unduly cautious in drawing our 

 conclusions. The bibliography has been much expanded, so as to cater for the 

 needs of those who use the book more as a work of reference than as a textbook. 

 For the increased length of the new edition we tender our apologies. The war 



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