444 BACTERIOPHAGES 



Introduction 



It is now generally agreed that the bacteriophage principle of 

 d'Herelle is a group of filtrable viruses, parasitic on bacteria and 

 more closely related chemically and physically to the animal vi- 

 ruses than to the plant viruses. Because of the ease with which 

 they and their host may be grown and studied, because of the 

 high precision with which they may be assayed and because a 

 single infected host cell may be readily isolated and observed in 

 the absence of interaction with other cells, the bacterial viruses 

 have become the subjects of widespread research as models of 

 the host- virus relationship. The bacterial viruses have been 

 used as tools in the study of the synthesis of proteins and nucleic 

 acids in infected cells, as a test system in the search for possible 

 chemo therapeutic and antibiotic agents for virus diseases, in 

 the study of the phenomenon of virus interference, in the study 

 of the action of ultraviolet light and X-radiation on viruses and 

 in the study of the mutational patterns of viruses and bacteria. 

 The possibilities inherent in the bacteriophage as a tool in the 

 study of relationship between virus and host cell have been 

 largely underrated. It is because of the greatly increased in- 

 terest in recent years in this group of viruses that it was thought 

 worth while to collect in one place the various techniques found 

 most suitable for research in this field. 



The author is greatly indebted to Prof. Max Delbriick for a 

 critical reading of the manuscript; many comments and sug- 

 gestions of his have been incorporated in the text. The author 

 is also grateful to S. E. Luria, R. Dulbecco, T. F. Anderson, 

 and A. H. Doermann for helpful discussions concerning certain 

 portions of the material. However, no one but the author is 

 responsible for any errors or omissions. Some of the photo- 

 graphs showing plaque morphology are included through the 

 kindness of Dr. Delbriick. The author's unpublished experi- 

 ments which have been included were aided by a gram from the 

 National Foundation for Infantile Paralysis, Inc. 



