124 THE BACTERIOPHAGE AND ITS BEHAVIOR 



million B. coli per cubic centimeter was obtained within a very short 

 time (3| hours) in an incubator at 46°C. In this experiment I did 

 not measure the rate of increase of the corpuscles but it is certain that 

 at the moment when bacteriophagy was complete the multiplication 

 must have been considerable.* 



Multiplication as affected by the state of the bacteria 



Doerr and Griininger^^^ have suggested that when the bacteriophage 

 is inoculated into an actively growing bacterial culture the bacteriophage 

 develops immediately, without a latent period. It has been impossible 

 for me to verify this, although I have made many experiments to this 

 end with bacteria of different species and with races of the bacteriophage 

 of diverse activities. Data on 21 such experiments are at hand, all 

 carried out in the same manner, inoculating the bacteriophage corpus- 

 cles into cultures containing about 50,000,000 bacteria per cubic centi- 

 meter, (faintly turbid) and incubated at 36°C. for 5 hours before the 

 introduction of the bacteriophage. Titrations of the bacteriophage 

 made every 15 minutes have shown the minimum time before which 

 the first increase was to be observed was 45 minutes, and indeed this 

 was obtained in only one of the experiments. On this occasion al- 

 though present, the increase was sHght (3-fold). In this same experi- 

 ment the bacteriophage had increased 39-fold after 60 minutes; 41-fold 

 after 75 minutes. In this single case the first rupture had taken place 

 after 45 minutes. The first series of ruptures was complete after 1 hour. 

 In 12 other experiments of this same type the first increase took place 

 after 60 minutes (4 races of Coli-bacteriophage, 5 of Shiga-bacterio- 

 phage, and 3 of Typhoid-bacteriophage; all very virulent races). In 

 the other 8 experunents the first increase could be detected only after 

 90 minutes. And in all of these, races of the Coli-bacteriophage of 

 relatively high activity were used. 



If we compare these experiments with the other results which have 

 been mentioned it appears that although multiplication may not 

 start immediately, the rate of reproduction may be accelerated when 

 the bacteriophage is inoculated into an actively developing culture. 

 While superficially this fact might appear to be significant, in reality 

 the result is simply due to the fact that the temperature is favorable 

 (37°C.) for the process at the moment of inoculation. If bacteria are 

 suspended in a bouillon previously warmed to 37°C. and this is inocu- 



* But they are weakened, as we will see. 



