118 THE BACTERIOPHAGE AND ITS BEHAVIOR 



reasons. The first step in the process is the approach of the corpuscle 

 to the bacterium (it can not be otherwise, since we know that 

 the corpuscle can only act after it is fixed), and the more distant a 

 corpuscle from the nearest bacterium the greater wiU be the time 

 required for the fixation. Furthermore, we will see that even in the 

 case of a bacteriophage of maximum potency all of the corpuscles do 

 not have an equal virulence. The rapidity of fixation to a given 

 bacterium, all of the other conditions being equal, is in direct propor- 

 tion to its "virulence." This represents a further reason why the 

 fixation of all of the corpuscles may be distributed over a certain period 

 of time. Recognizing these facts, it is clear that the best condition 

 for observing the true nature of the reaction consists in inoculating at 

 the beginning only a very small number of corpuscles, so that complete 

 fixation can be accomplished in a minimum of time. As a result of this 

 all of the ruptures, and consequently the liberations of young corpus- 

 cles, will occur after a like interval of time. This will permit one to 

 observe that multiplication, the increase in the number of corpuscles, 

 takes place suddenly. 



Another requisite condition, already mentioned, involves the presence 

 of a large number of bacteria. The significance of this factor is evi- 

 dent, for if there is only a small number each bacterium will be found at 

 a considerable, and very variable, distance from the nearest corpuscle. 

 This again means that fixation will occur in a very irregular manner. 



With due regard to the conditions mentioned anyone may demon- 

 strate readily that the multipHcation of bacteriophage corpuscles 

 takes place by means of successive jumps and not in a gradual pro- 

 gressive fashion. But even here, this fact can be shown definitely 

 only for the first hberation, as is quite natural, since as bacteriophagy 

 progresses the greater will become the number of corpuscles, and the 

 virulence of each of them, as individuals, being different, the time of 

 fixation, and consequently, the speed of multipHcation, will proceed 

 in an irregular manner.* The multipHcation by successive jumps, 

 extremely clear-cut in the beginning of the process, becomes with time 

 less and less sharply defined. The first series of Hberations of the 

 young corpuscles is accompHshed within a short time, while for the 



* This fact is not astonishing. We have known since the days of Pasteur that 

 in a bacterial culture each of the organisms presents individual characteristics, 

 chiefly in those attributes dealing with its virulence. In the chapter devoted to 

 "The Virulence of the Bacteriophage" we will see that the situation is exactly 

 the same with the bacteriophage. 



