356 



F. W. STAHL 



Chapter V, Volume I, should be referred to for a somewhat fuller discus- 

 sion of target theory and of the factors which modify the constant yt^. 



These brief remarks on the three radio-agents and the theoretical frame- 

 work within which they will be considered must suffice as introduction to 

 this review. From this point on, our purpose will be best served by a con- 

 sideration of one of these agents (ultraviolet light) with emphasis of its 

 effects on one or the other of a pair of closely related phages (T4 or T2). 



Time of irradialion (.secj 



100 200 300 



Fig. 1. A "one-hit" survival curve. The logarithm of the fraction of phage retaining 

 the ability to form plaques as a function of the dose of X-rays is linear. The data are for 

 the survival of T6 exposed to soft X-rays in concentrated broth. 



With this system the basic problems of radiobiology of phage have been 

 raised; within this system some of these problems show promise of being 

 answered. By means of this system the reader will become acquainted with 

 a way of thought which at present appears the most promising for analyzing 

 the effects of radiation on bacterial viruses.^ Following this baptism, we shall 

 look at the effects of other agents, and the responses of other phages. The 



^ Perhaps one could equally well introduce the problems of phage radiobiology by 

 detailing our knowledge of the effects of ultraviolet light on the phage A (see especially 

 Jacob and Wollman, 1955 and Kellenberger and Weigle, 1958). The present choice was 

 to some degree governed by the author's greater familiarity with the T-phages. 



