PREFACE TO THE ENGLISH EDITION 



The present English edition of the monograph which presents 

 the results of my investigations on the Bacteriophage is not a 

 simple translation of the French edition, which, appearing in 

 October, 1921, was one of the series of monographs of the Pasteur 

 Institute. The bibliography has been extended, and in many 

 of the chapters new experimental evidence has been introduced, 

 embodying work completed since the publication of the French 

 edition. In addition, a wholly new chapter has been prepared 

 dealing with the " Nature of the Bacteriophage/ ' which pre- 

 sents a statement of and an analysis of the diverse hypotheses 

 which have been advanced in explanation of the intimate nature 

 of the principle. Indeed, and this is of some significance, this 

 is the only point — purely theoretical moreover — upon which dis- 

 cussion of the subject turns. As for the experimental facts 

 themselves, they have never been questioned, for all investiga- 

 tors who have worked with the bacteriophage have confirmed the 

 experimental results almost in their entirety. 



It is my hope that this work will be of interest to the biologist. 

 I hope especially that it will stimulate American bacteriologists 

 in greater and greater numbers to become interested in investiga- 

 tive work upon the subject; one which is new and which promises 

 to be fruitful in theoretical and practical results. And this is 

 my wish the more since, although working for many years in 

 France, the signatory of these lines in the quality of a Canadian, 

 feels himself a part of the great American family. 



March 15, 1922 



