BACTERIOPHAGY IN A FLUID MEDIUM 73 



These observations may be summarized very simply, then, by stating 

 that bacteriophagy is operative only with living and nonnal bacteria. 



8. PHENOMENA CORRELATIVE WITH BACTERIOPHAGY 



Acceleration of bacterial growth 



We have ah-eady seen, in the experiments described, that if a sus- 

 pension of bacteria is inoculated with a relatively small amount of 

 bacteriophage, the bacteria develop, as revealed by the increasing 

 turbidity, and it is only after this initial growth that the bacteria 

 commence to dissolve. But if the experiments described above be 

 carefully watched something else may be observed, namely, that the 

 growth is more rapid, often very much more so, in the suspensions where 

 bacteriophagy is to take place than in the control suspensions uninoc- 

 ulated with the bacteriophage. It would seem that the presence of 

 this dissolving principle applies a stimulus of some sort, as though the 

 multiplication of the bacteria undergoes first a "speeding-up;" an 

 acceleration of the processes of cellular division. 



Agglutination 



Very often it may be observed that dissolution of the bacteria is 

 preceded by a very outspoken agglutination. This phenomenon is par- 

 ticularly marked when the bacterial suspension is inoculated with a 

 relatively large amount of bacteriophage filtrate of average potency 

 (d'Herelle^^i). 



Sometimes this agglutination takes place very quickly, even within 

 a few minutes after the bacteria come into contact with the bacterio- 

 phage. The cause of this agglutination does not appear to reside in 

 the bacteriophage principle itself, but in "a something" which is as- 

 sociated with it in the filtrate. The following experiments show, in 

 fact, that this agglutination takes place in physiological saline, and 

 even if the bacteria are killed previously by heat. The agglutinating 

 substance passes through colloidion membranes that are relatively 

 open, and it resists ageing. 



A bacteriophage filtrate, about 6 months old, active for B. dysenteriae 

 Shiga, was diluted to 1 : 1000 in physiological sahne and dialyzed, in a 

 collodion sac, against physiological saline. After dialysis for 48 hours 

 living Shiga bacilli, taken from a young agar culture, were suspended in 

 the dialysate, yielding a suspension containing 100 milHon organisms 



