A. H. DOERMANN 651 



lysing medium. In fact, during the second half of the latent period, phage 

 liberation is identical in the two media. 



In order to see whether lysis is actually occurring and can account for the 

 liberation of phage, a nephelometric experiment was made introducing CN~ at 

 two points in the latent period. Three cultures of B/r/1 growing exponentially 

 in growth medium were infected with T4r48 (ca. fivefold multiplicity). One 

 culture served as a control for normal lysis. To the second culture cyanide (0.01 

 M final concentration) was added 7.5 minutes after addition of the virus and to 



CN~ADDEDT0 2 T4i. AT 37° 



10 20 30 40 50 60 70 80 90 290 



MINUTES AFTER ADDITION OF PHAGE TO BACTERIAL CULTURES 



Fig. 3. The turbidity of T4-infected bacterial cultures as affected by addition of 

 cyanide at two stages in the latent period. 



the third tube 17.5 minutes after addition of the T4r48. The turbidities of these 

 three cultures were followed with a nephelometer designed like that described 

 previously by Underwood and Doermann (8), but with four separate units 

 which permit independent readings on the four tubes without removing any of 

 them from the instrument. The results indicate that CN~ added to infected 

 bacteria early during the latent period does not induce lysis (Fig. 3). From the 

 plaque count experiment (Fig. 2) it is seen that a loss of infective centers does 

 occur. This loss must therefore be due to some cause other than lysis of these 

 cells. In the later stages of the latent period, the turbidimetric experiment 

 indicates that lysis occurs promptly upon the addition of CN~ to the culture 



81 



