106 THE BACTERIOPHAGE AND ITS BEHAVIOR 



After 30 minutes the corresponding counts are; 201 and 211. 



After 1 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 

 nothing happens. The corpuscles remain inert in the medium. 



The nature of the multiplication taking place in the presence of the 

 Shiga bacillus does not permit of any doubt on the following points: 



1. After a contact of 30 minutes at 37°C. the corpuscles have almost 

 entirely disappeared from the fluid; they are fixed by the bacteria. 

 After 1 hour the situation is essentially the same. 



2. The fixation is elective. It does not occur with V. cholerae, for 

 example, for which the bacteriophage in question is without action 

 (d'Herelle^^i)^ 



A complementary experiment, conducted in the same fashion, but 

 centrifuging the suspension at 10-minute intervals during the first 

 half-hour, has shown that very few of the bacteriophage corpuscles 

 are fixed during the first 10 minutes, although they are almost all fixed 

 after 20 minutes. The union, therefore, requires about a quarter of 

 an hour. 



Additional data obtained with the staphylococcus may be introduced 

 as bearing upon this subject of fixation. Ten cubic centimeters of a 

 normal suspension of cocci are combined with 0.1 cc. of the bacterio- 

 phage suspension. The temperature is held throughout at 30°C. 

 With this particular race of bacteriophage, of relatively high but not 

 of maximum potency, the fluid still contains 97 per cent of the intro- 

 duced corpuscles after 45 minutes. After 1 hour 62 per cent are pres- 

 ent; after 75 minutes, but 8.5 per cent remain. 



On the other hand, with two races of the bacteriophage of maxiinum 

 potency the fixation was extremely rapid. When 0.1 cc. of a suspension 

 containing 20,000 million corpuscles per cubic centimeter was intro- 

 duced into 10 cc. of bacterial suspension (250 million cocci per cubic 

 centimeter) and the material was filtered through a candle after 10 

 minutes there was not a single corpuscle in 0.05 cc. of the filtrate. The 

 fixation was complete. 



This experiment shows particularly well how the activity of the 

 bacteriophage race influences the speed of fixation. 



The fixation of the bacteriophage corpuscle to the susceptible bac- 

 terium constitutes then, the first act of bacteriophagy (d'Herelle'^''' ^'O- 

 This fact is accepted by all authors. The only difference to appear in 



