120 THE BACTERIOPHAGE AND ITS BEHAVIOR 



and multiplies the more rapidly as its "virulence" is the greater. But 

 it is equally important to observe that against different bacterial 

 species bacteriophage races of the same degree of virulence may be- 

 come fixed and may multiply at different rates. 



From the experiments which I have carried out upon this subject 

 the following may be cited as giving the maximum and minimum 

 rates observed. 



With the most active race of Shiga-bacteriophage which I 

 have isolated the fixation amounted to 94 per cent after -12 minutes 

 (10,000 corpuscles per cubic centimeter in the presence of 250,000,000 

 bacteria per cubic centimeter) at a temperature of 30°C. Inoculating 

 a single corpuscle into 10 cc. of a suspension containing 50,000,000 

 bacteria per cubic centimeter there were, after 11 hours, 12,000 million 

 corpuscles per cubic centimeter. 



With a Shiga-bacteriophage of low activity, in inoculating 100,000 

 corpuscles into 10 cc. of a suspension containing 250,000,000 bacteria 

 per cubic centimeter after 20 minutes only 10 per cent had been fixed. 

 Here also the temperature was 30°C. After 60 minutes only 34 per 

 cent had been fixed. Inoculating a single corpuscle into 10 cc. of a 

 suspension containing 250,000,000 bacteria per cubic centimeter there 

 were, after 24 hours, only 17,000,000 corpuscles present in the liquid. 



With an extremely potent race of the Staphylo-bacteriophage, work- 

 ing under the same conditions as those described for the active Shiga- 

 bacteriophage, the fixation was complete 20 minutes after the inocula- 

 tion. Inoculating a single corpuscle into 10 cc. of a suspension con- 

 taining 50,000,000 bacteria per cubic centimeter* the maximum value 

 was reached only after 44 hours, and at this time there were 98,000 

 milHon corpuscles per cubic centimeter. 



Working under the same conditions as those of the preceding experi- 

 ment, but using another race of Staphylo-bacteriophage, one much 

 less potent, the fixation after 75 minutes amounted to 54 per cent. A 

 single corpuscle inoculated into a suspension of staphylococci contain- 

 ing 50,000,000 per cubic centimeter yielded, after 48 hours, only 

 780,000,000 corpuscles per cubic centimeter. 



In bacteriophagy the result of a single experiment always depends 

 upon the conditions of the experiment, the most important of these 



* We have seen in Chapter I that in inoculating a very small amount of bac- 

 teriophage the initial number of bacteria is of little consequence, for the latter 

 develop abundantly up to the moment when the multiplication of the bacterio- 

 phage is sufficient to effect bacteriophagy of all of the bacteria. 



