BACTERIOLYSIS 55 



Experiment XII. Tubes of bouillon, containing glycerine in the fol- 

 lowing concentrations, are seeded with a drop of an eighteen-hour bouillon 

 culture of B. dysenteriae Shiga. The results secured with the different con- 

 centrations are: 



Bouillon -f 5 per cent of glycerine : Very abundant growth 

 Bouillon + 10 per cent of glycerine: Weak growth 

 Bouillon + 15 per cent of glycerine: Very slight growth, with sedi- 

 ment 

 Bouillon + 20 per cent of glycerine : Clear medium, with abundant 



sediment of bacteria 

 Bouillon + 25 per cent of glycerine: Clear medium, slight sediment 

 Bouillon + 30 per cent of glycerine: Clear medium, slight sediment 

 Bouillon + 35 per cent of glycerine: Clear medium, trace of sediment 

 Bouillon + 40 per cent of glycerine : No growth whatever 

 All subcultures made from these tubes at the end of forty-eight hours 

 give, in normal bouillon, normal growths. 



B. typhosus is somewhat more sensitive to the action of glycerine. Even 

 in a medium containing 10 per cent the growth is insignificant. 



Bacteria suspended in glycerine bouillon, even in a concentra- 

 tion of 25 per cent, remain alive for at least forty-eight hours; 

 that is, throughout a time amply sufficient for the bacteriophage 

 to develop and to effect lysis, as was the case with the fluoride 

 medium. But the following experiments show that the culture 

 of the bacteriophage in the glycerine medium is absolutely nor- 

 mal while it is entirely lacking in the fluoride medium. 



I emphasize the fact of the growth of the bacteriophage and 

 the lysis which is the result of this growth in a glycerine medium, 

 for it will be necessary to return to these experiments when we 

 review the various proofs concerning the living nature of the 

 bacteriophage. 



Experiment XIII. Tubel. Prepare a suspension of B. dysenteriae 

 Shiga, 250,000,000 per cubic centimeter, in bouillon containing 35 per cent 

 of glycerine. Inoculate with 0.02 cc. of the bacteriophage culture. Nor- 

 mal lysis occurs in eight hours. A control suspension of the Shiga bacilli 

 in the glycerinated medium, but without the bacteriophage, yields positive 

 subcultures up to the seventh day. 



Tube 2. Shiga bacilli, 250,000,000 per cubic centimeter, are suspended 

 in bouillon with 50 per cent glycerine. The medium is inoculated with 0. 02 

 cc. of the bacteriophage. Normal lysis takes place in ten hours. The 

 control suspension, without the bacteriophage, is cultivable up to the 

 forty-eighth hour. 



