152 THE BACTEKIOPHAGE 



tically, their number varies from tube 1, which had received the largest 

 amount of bacteriophage culture, to tube 10, which had received the 

 smallest, in the proportion of 10:9:8:7:6:5:4:3:2:1. 



These two experiments, which complement each other, demon- 

 strate unquestionably, that the active principle is contained 

 solely in the filtered culture of the bacteriophage; and that this 

 active principle is composed of material elements, capable of 

 forming colonies on agar at the expense of the surrounding bac- 

 teria in such a way that their enumeration is possible. These 

 material elements are capable of multiplication as is shown by 

 the formation of colonies and by action in series. It can thus 

 only be a living organism. This experiment by itself is sufficient 

 to demonstrate that the bacteriophage is a " formed ferment," 

 which in reality implies the existence of an ultramicrobe parasitic 

 of the bacteria. 



5. Eliava and Pozerski have shown that toward concentra- 

 tions of free H and OH ions the range fatal for the bacteriophage 

 is more limited than for the bacteria. The diastases and toxins 

 react in a wholly different fashion. 



6. Dumas, confirmed by Beckerich and Hauduroy, have iso- 

 lated the bacteriophage from the soil and from the filtered water 

 of streams. I have myself isolated it from sea-water. There is 

 nothing strange in this, since it is an ultramicrobe derived from 

 stools. This fact can not, on the contrary, be reconciled with a 

 hypothesis of a ferment, whether the ferment be of leucocytic or 

 other origin. 



7. Diastases in solution are absorbed by the precipitates which 

 form upon the addition of alcohol. This takes place with cul- 

 tures of the bacteriophage, but the elements which precipitate are 

 not the ultramicrobes themselves. The ultramicrobes are de- 

 stroyed by the alcohol, and the principle which is precipitated 

 will not reproduce the action in series. This possibility of ex- 

 tracting from a culture an active principle which can only be a 

 secretory product of the bacteriophage shows indeed that the 

 latter can be nothing other than a living being. 



8. I have shown that the bacteriophage is capable of adaptation 

 to the harmful action of glycerine. Adaptation is the appanage 

 of living beings exclusively. 



