338 THE BACTERIOPHAGE AND ITS BEHAVIOR 



bacteriophage (that is, the material added to the first suspension to 

 induce bacteriophagy) can remain. As we know, this degree of dilu- 

 tion can be calculated. Physicists have determined that the smallest 

 particle of matter is the electron, whose mass is 1-10~" grams. When, 

 as a result of successive dilutions, we introduce into one of the tubes of 

 the series a quantity less than I-IO"^^ gram of the initial bacteriophage 

 filtrate, we may be sure that we no longer have any of the initial filtrate, 

 and consequently, none of the bacteriophage corpuscles (in the present 

 experiment, bacteriophage h) inoculated in the first suspension of the 

 series. 



Still another precaution should be taken, namely, to heat, at 60°C., 

 the bacteriophage filtrate inoculated into the first suspension (here. 

 Staphylococcus albus V). This eliminates the possible objection that 

 this filtrate might have contained some filtrable form of the bacterium 

 {Staphylococcus aureus) which, being inoculated in the first passage, 

 might persist throughout the whole series, and which, indeed, may be 

 the organism at whose expense the bacteriophage multiples and per- 

 sists in its poly virulence.* 



Bearing these things in mind, this experiment was performed. In 

 each of the successive passages 10 cc. of a staphylococcus V suspension 

 was inoculated with 0.001 cc. of a bacteriophage h suspension, and the 

 series was continued, the quantitative relationships being the same, the 

 bacterial suspension being freshly prepared from the same strain, and 

 the bacteriophage suspension being in every instance a heated filtrate of 

 the last suspension dissolved. As we have shown elsewhere, in the 

 seventh suspension of the series the degree of dilution of the initial 

 suspension of bacteriophage is 1-10~-^, that is to say, in the present 

 experiment 1 cc. of the seventh suspension can contain but 1-10~-^ 

 grams of the original suspension of bacteriophage h. Such a quantity 

 is imaginary and represents nothing real, since it is smaller than an elec- 

 tron. It is certain, therefore, that the eighth suspension of staphylococ- 

 cus V will not receive any of the original bacteriophage h corpuscles. 

 When the dissolution of the organisms of this eighth suspension is 

 completed all of the corpuscles present will be those which must have 

 reproduced at the expense of the Staphylococcus albus V. But, experi- 

 ment shows that the bacteriophage corpuscles of this eighth suspension, 

 when bacteriophaged, as also are those present in the fifteenth when the 



* In repeating this experiment I have taken the precaution, not only to filter 

 and to heat at 60°C. the first suspension of bacteriophage h, but I have repeated 

 both of these procedures with each of the 15 passages. 



