ANTIGENIC PROPERTIES 113 



data and discussion of these effects are given by Cann and Clark 

 (1954, 1955). 



Hershey (1941) discussed the absolute rate of the phage- 

 antiphage reaction, giving theoretical equations from which 

 the maximum rate could be calculated. The calculations and 

 some of the discussion in this paper are incorrect because of 

 erroneous concepts of the nature and size of phage T2 current 

 at that time. However, recalculation using Hershey's methods 

 and more modern data indicates that the actual inactivation 

 rates observed by Jerne are of the same order of magnitude as 

 the maximum rate attainable assuming that every collision 

 resulted in antibody attachment. Control of the ionic environ- 

 ment and the use of cofactors in Jerne's experiments resulted 

 in increasing the number of effective collisions between anti- 

 body molecules and susceptible sites on the phage particle to 

 nearly the theoretical limit. 



A theoretical analysis of the neutralization of T4 is given by 

 Mandell (1955). 



10. Anomalous Neutralization Behavior 



A fact which puzzled Andrewes and Elford (1933a) was that 

 neutralization of their phages proceeded rapidly until 90 to 

 99 per cent of the phage was inactivated and then slowed down 

 rather abruptly, the residual phage activity appearing to be 

 very resistant to neutralization. They demonstrated that this 

 could not be due to exhaustion of antibody and hence must be 

 due to inhomogeneity of the phage population with respect to 

 susceptibility to inactivation. That this inhomogeneity was 

 not genetic in origin was demonstrated by subculturing plaques 

 of phage particles which had survived treatment with antiserum. 

 The descendants proved to be normally susceptible to neutraliza- 

 tion by antiserum. 



The possibility that the inhomogeneity was caused by the 

 action of antiserum itself, combining with the phage particles 

 in such a way as to make them resistant to neutralization, was 

 next considered. This possibility was discarded because the 



