102 THE BACTERIOPHAGE AND ITS BEHAVIOR 



question when we have studied the effect of an antibacterial serum 

 upon the phenomenon of bacteriophagy. Here let us simply say that 

 it is probable that this anomaly consists in a modification of the sur- 

 face tension of the bacterial cell. 



We have seen above that the bacteriophage corpuscle multiplies 

 only in the presence of living and normal bacteria. While this is in 

 general true, it is likewise true that under very particular conditions, 

 as observed by Wollman,^^- a certain amount of bacteriophage develop- 

 ment appears to take place in the absence of intact bacterial cells. This 

 investigator prepared a series of collodion sacs of different densities, 

 thus regulating the permeability.* After sterihzation he filled the 

 sac, having a capacity of 6 cc, with a bouillon implanted with Shiga- 

 Kruse bacilli. In the outer tube, within which the sac was suspended, 

 he placed 20 cc. of bouillon containing bacteriophage filtrate. The con- 

 centration of bacteriophage in this external fluid was such that when 

 10 cc. of a suspension of B. dysenteriae was inoculated with 1 drop of 

 the fluid and 1 drop of the resulting mixture was spread upon agar but 

 two plaques would form. 



In this way he prepared a series of collodion sacs of increasing per- 

 meabihty, all arranged in the same manner, with a suspension of 

 B. dysenteriae within the sac and a bouillon suspension of the bacterio- 

 phage in the tube into which the sac was immersed. 



After incubation he observed the following: 



Very -permeable sacs. It will be recalled that, as I had shown pre- 

 viously,^^^ the bacteriophage corpuscle passes through collodion mem- 

 branes which are sufficiently permeable to permit the passage of the 

 molecule (perhaps it would be better to say micella) of serum albumin. 

 In this experiment of Wollman the same fact appears, for he found that 

 the corpuscles passed through the permeable membranes, penetrating 

 into the sac. There coming into contact with the dysentery bacilli 

 they caused bacteriophagy, as would be expected. 



Less permeable sacs. With these sacs the baclilary culture within 

 the sac remained normal, but the number of corpuscles inoculated into 

 the bouillon surrounding the sac increased. A preliminary test showed, 

 as we have seen, that a drop of the bouillon outside gave two plaques 

 on agar. After incubation, a test conducted in the same manner 

 with the same amounts, yielded from 20 to 30 plaques. There were, 

 then, from 10 to 15 times as many corpuscles after incubation as be- 



* For the methods of preparation and arrangement of collodion sacs see the 

 section "Ultrafiltration" in the Introduction. 



