X PREFACE TO SEVENTH EDITION 



The keys to the several categories of taxa (orders, families, tribes, genera and 

 species) have been revised with a view to making them more reUable and useful. 

 There is included also an artificial key to the species prepared by Professor 

 V. B. D. Skerman, which key should prove helpful. 



The Section on Nomenclature, including a synopsis of the Botanical Code of 

 Nomenclature, has been eliminated. At the time of preparation of the sixth 

 edition, the International Code of Bacteriological Nomenclature had not been 

 finally approved, and emphasis was properly laid upon the rules used in Botany. 

 This is no longer pertinent. The Bacteriological Code appeared in 1948 too late 

 for use in making appropriate revisions in the 6th Edition of the Manual. The 

 revised International Code of Nomenclature of the Bacteria and Viruses is about 

 to be published. This contains annotations that should prove of value to the 

 student, and should be regarded as a helpful aid in the understanding of the 

 nomenclature used in the 7th Edition of the Manual. 



The naming and classification of the viruses, as published in the sixth edition 

 of the Manual, was regarded by some eminent virologists as perhaps inadvisable 

 because it was premature. They felt strongly that the problems of morphology, 

 physiology, pathogenesis and inter-relationships of the viruses were not as yet 

 sufficiently resolved to make satisfactory taxonomy and classification practicable. 

 After consultation with the International Subcommittee on Viruses it was de- 

 cided that the Virus Section should not be included in the seventh edition. This 

 deletion has been made with the full expectation that sufficient international 

 agreement will be reached to make possible adequate treatment in the eighth 

 edition. The Editorial Committee recognizes that a satisfactory system of 

 nomenclature and taxonomy for the viruses is imperative. 



The Editors wish to repeat and emphasize a statement made in the Preface 

 of the first edition of the Manual: 



"The assistance of all bacteriologists is earnestly solicited in the correction of possible 

 errors in the text." 



Among the tasks of the several editions of the Manual has been the codification 

 of an increasingly satisfactory classification of the bacteria and the correction of 

 the nomenclature of the past. The present volume undoubtedly has many errors 

 that were not caught notwithstanding a most earnest effort. There are also many 

 unresolved questions. Inasmuch as this volume appears at almost the same time 

 as the Revised International Bacteriological Code, there are doubtless still some 

 inconsistencies. 



E. G. D. Murray 

 N. R. Smith 

 R. S. Breed, Chairman 

 Editorial Committee 



