60 THE BACTERIOPHAGE 



1 : 18. And this increase has taken place in apparently a very abrupt man- 

 ner, only to be explained as a result of the liberation of actual colonies 

 containing an average of about 18 germs. We will see by ultramicro- 

 scopic examination that the lysis of a parasitized bacterium takes place 

 brusquely, by bursting. 



Tube 2. Control. Suspension of V. cholerae plus the bacteriophage. 



Counts made immediately after inoculation of the bacteriophage give: 

 for the centrifuged material 201, for the non-centrifuged, 211 plaques. 



After thirty minutes the counts are : for the centrifuged, 210; for the non- 

 centrifuged, 216. 



After one hour the counts are: for the centrifuged, 203; for the non- 

 centrifuged, 199. 



After one and one-half hours the non-centrifuged suspension gives 207. 



Tube 3. Control. Sterile bouillon plus the bacteriophage. The 

 counts immediately after the inoculation are: for the centrifuged, 206; 

 for the non-centrifuged, 210. 



After thirty minutes the corresponding counts are: 201 and 211. 



After one hour, the counts are : 203 and 206. 



After one and one-half hours the non-centrifuged medium contains 198. 



As is evident, in the absence of bacteria capable of being attacked, noth- 

 ing happens. The ultramicrobes remain inert in the liquid. 



The nature of the multiplication taking place in the presence 

 of the Shiga bacillus does not permit of any doubt on the follow- 

 ing points. 



1. After a contact of thirty minutes at 37°C. the ultramicrobes 

 have almost entirely disappeared from the fluid; they are fixed 

 by the bacteria. After one hour the situation is essentially the 

 same. 



2. After one and one-half hours there is an abrupt increase in 

 the number of the bacteriophagous ultramicrobes. 



3. The fixation is elective; it does not occur with V. cholerae, 

 for example, for which the bacteriophage in question is without 

 action. 



From this it may be concluded that the culture of the ultrami- 

 crobes takes place within the interior of the bacillary body, and 

 all the other observed facts support this conception based upon 

 experiment. We can now understand the cause for the successive 

 jumps noted in the culture of the bacteriophage, mentioned pre- 

 viously in connection with the multiplication of the germs. Each 

 of the ultramicrobes inoculated penetrates to the interior of a 

 bacillus and there multiplies up to the time when the bacillary 



