126 



BENZER ET AL. 



TIME (MIN.) 

 Fig. 2. Premature lysis of B/r/i cells infected with T3, at various 

 stages of the latent period. The percent of the final yield of phage 

 as function of the time of incubation at 30C after infection. 

 Curve I: Infected cells disrupted after incubation by sonic vibration. 

 Curve II: Control one-step growth curve. 



the infecting particles may however be due to secondary causes.) If, 

 on the contrary, a bacterium is infected with high multiplicity of un- 

 labelled phage and grown in medium containing P^% the phage appear- 

 ing in the yield shows the specific activity of the medium without dilu- 

 tion from the cold phosphorus of the infecting particles (Hershey, per- 

 sonal communication). 



VI. Mixed Infection 



29. Mixed infection with particles differing by one mutational 

 step. — Experiments of this type were performed with the mixture 

 T2+T2r. The yield of a bacterium infected with the two types 

 contains particles belonging to both types. On the average the pro- 

 portions in the yield are equal to the proportions among the infect- 

 ing particles (Hershey, 1946). 



