520 BACTERIOPHAGES 



was the metabolic poison, and phage T6 was used to hberate 

 the T4 phage by lysis from without. The lysing medium was 

 the growth medium plus O.OlAf KCN and 4X10'-' T6 particles/ 

 ml. All assay platings were by the agar layer technique on B/6, 

 since this indicator strain permits assay of T4 in the presence 

 of T6. A culture of B was grown to 10^/ml. and concentrated 

 to 10^/ml. so that phage adsorption would be rapid. A stock 

 of T4r phage was diluted to 10^/ml. in the growth medium. 

 Anti-T4 serum diluted in the growth medium was used to neu- 

 tralize free phage. 



Protocol 



Platings made at intervals from F.G.T. and S.G.T. gave the 

 usual one-step growth curve which was used as a control on 

 latent period and burst size. 



At intervals during the latent period 0.1 ml. samples from the 

 dilution tube were diluted into 1 .9 ml. samples of the lysing medium 

 chilled to 0° C., kept cold for 10 min., then incubated for 30 

 min. at 37 ° C. The chilling and the KCN in the lysing medium 

 interrupted phage growth, and the high concentration of T6 

 phage brought about lysis from without, liberating any T4 

 phage which had been produced up to the time of dilution 

 into the lysing medium. After the 30 min. incubation period 

 an aliquot of each lysing medium tube was plated on B/6 to 



