72 THE BACTERIOPHAGE 



In the following experiment the most powerful strain of the 

 bacteriophage yet isolated is made to act upon two different races 

 of the Shiga bacillus. One of these bacterial strains has been for 

 a long time under artificial cultivation, being used by the Pasteur 

 Institute for the inoculation of horses in the production of anti- 

 dysentery serum (type strain). The other was recently isolated 

 from the stool of a patient with dysentery (strain Jerv.). 



Experiment XVIII. (A) Twelve tubes of the suspension of the type 

 strain of the Shiga bacillus are each inoculated with 0.001 cc. of a culture 

 of the bacteriophage. This latter has been carried on for a great number 

 of generations always at the expense of a single bacillary strain. In all 

 twelve tubes lysis is perfect, with complete clearing in four hours. After 

 three days at 37C. one of the tubes is slightly cloudy, the others are clear, 

 (Five other experiments, each consisting of 12 tubes, with the same strain 

 of bacteriophage and the same bacillus give the following results: tubes 

 showing secondary cultures in each set, 0, 2, 0, 3 and 1. There develop, 

 then, 7 secondary cultures in the 60 tubes, or 12 per cent.) 



(B) Twelve tubes of suspension were prepared with the strain Jerv., a 

 strain with which the bacteriophage in question had never been in contact. 

 Each of these tubes is inoculated with 0.001 cc. of the same culture of 

 bacteriophage as that used in the preceding experiment (A). Seven 

 of the 12 tubes give secondary cultures. The results from five other experi- 

 ments with the same strains are, 9, 5, 10, 5, and 6 secondary cultures, or 

 70 per cent. A week later 12 cultures of the Jerv. bacillus are inoculated 

 from one of the previous tubes that had remained clear. From these, 5 

 secondary cultures are secured. 



A further passage made after another week, gives 4 secondary cultures 

 in the 12 suspensions. After another week, a fourth passage, still taking 

 the bacteriophage from a perfectly limpid culture, yields but one secondary 

 culture among the twelve inoculated. 



(C) At the beginning of convalescence in the dysentery case (Jerv.) 

 a bacteriophage was isolated which was tested in the same manner both 

 on the type Shiga strain and on the Jerv. strain. This last was derived 

 from the patient early in the infection at a time when the intestinal bac- 

 teriophage had manifested no activity for this organism. 



With the bacteriophage Jerv. on the type bacillus 4 secondary cultures 

 develop among the 12 suspensions lysed. 



With the bacteriophage Jerv. on the bacillus Jerv., there are no sec- 

 ondary cultures among the 12 tubes lysed. When repeated upon an addi- 

 tional 12 suspensions a single secondary culture develops. 



It is then clear that the anti-Shiga bacteriophage is not equally 

 active for all strains of B. dysenteriae Shiga. This fact is even 

 more in evidence with other bacterial species, for example, with 



