18 INTRODU CTION 



However that may be, the intensity of the bacteriophagous 

 action is sometimes of such violence that it must have been ob- 

 served by many bacteriologists in the course of their investiga- 

 tions even though the nature of the phenomenon and its mechan- 

 ism were not understood. For example, I have been informed 

 that in Haffkine's laboratory, it has been noted several times that 

 cultures of the plague bacillus in bouillon underwent clarification, 

 the medium becoming perfectly limpid within the space of a few 

 hours. Not knowing the reason for this curious phenomenon the 

 cultures were termed " suicides." For such reactions the bac- 

 teriophage was certainly the cause. 



Another observation of the same nature is reported by Eliava, 

 who, being in charge of the examination of the water of the Koura 

 river at Tiflis, noted the following phenomenon. The suspected 

 water under examination was added to a peptone solution. After 

 a few hours of incubation a specimen taken from the surface of 

 the medium for microscopic examination showed very numerous 

 vibrios of normal morphology. Planted upon agar, this speci- 

 men yielded upon incubation a growth of dull appearance which 

 microscopically appeared to be a culture of vibrios. Twelve 

 hours later, in so far as the peptone water was concerned, all 

 trace of the vibrios had disappeared. This experiment, repeatedly 

 performed, always gave the same result; it was impossible to 

 secure a culture of the vibrio. Although starting a normal de- 

 velopment, later, within a few hours, the vibrio had disappeared. 

 This phenomenon remained unexplained until the findings with 

 reference to the bacteriophage were published. 



In fact, it is certain that a large number of bacteriologists, 

 indeed, it may be said all bacteriologists, and reasons for this 

 statement will appear in the course of this discussion, have 

 accidentally encountered this strange phenomenon. Seen at 

 times in a fluid medium, at other times on a solid medium, such 

 reactions have repeatedly been observed but their study has been 

 neglected since their importance was not recognized. 



FUNDAMENTAL EXPERIMENT 



The experiment which served as a point of departure for sub- 

 sequent work was as follows. An adult, suffering with a severe 



