534 THE BACTERIOPHAGE AND ITS BEHAVIOR 



had been subjected to bacteriophagy for six hours was injected intra- 

 venously. (The amount of bacillary substance here was the same as 

 in the preceding.) The rabbit Hved. 



Rabbit No. 4. Two cubic centimeters of a Shiga culture which had 

 been undergoing bacteriophagy for six hours were injected subcutane- 

 ously. The animal died on August 16. This rabbit had also been 

 injected on August 10. 



Six days after the completion of the dissolution the toxicity of the 

 culture was markedly diminished, as the following tests show: 



Rabbit No. 5. Two cubic centimeters of a Shiga bacillus culture 

 which had been dissolved 6 days previously were injected intravenously 

 on August 10. The animal lived. 



Rabbit No. 6. Three cubic centimeters of the Shiga culture which 

 had been dissolved for 6 days were injected subcutaneously on August 

 10. This rabbit also lived. 



Rabbit No. 7. Five cubic centimeters of the Shiga culture which 

 had been dissolved for 6 days were injected intravenously on August 

 10. The rabbit died on August 21. 



When the tests were done with a Shiga culture which had been dis- 

 solved for a month the toxicity had disappeared, as is shown by the 

 following. 



Rabbit No. 8. Fifteen cubic centimeters of Shiga culture which had 

 been dissolved for one month were injected subcutaneously. The 

 rabbit lived. The injection was given on August 10. 



Rabbit No. 9. Ten cubic centimeters of this same preparation were 

 injected intravenously on August 10. This rabbit lived. 



The following protocol illustrates an immunization experiment. 



On August 23, eight rabbits received a subcutaneous injection of 0.25 

 cc. of a suspension of the Shiga-bacteriophage, two months after the 

 dissolution was completed. These animals were tested by the injection 

 of 3 cc. of a twenty-four hour bouillon culture of Shiga bacilli. For 

 the strain employed this represented two surely fatal doses. The strain 

 of Shiga used in the test differed from that used to prepare the suspen- 

 sion dissolved by the bacteriophage. 



Rabbit No. 10; tested after twenty-eight hours. Died six days later. 



Rabbit No. 11; tested after four days. Died five days later. 



Rabbit No. 12; tested after six days. Lived. 



Rabbit No. 13; tested after eight days. Lived. 



Rabbit No. 14; tested after ten days. Lived. 



Rabbit No. 15; tested after one month. Lived. 



